Quarterly report pursuant to Section 13 or 15(d)

Debt and Secured Revolving Line of Credit (Narrative) (Details)

v3.7.0.1
Debt and Secured Revolving Line of Credit (Narrative) (Details)
3 Months Ended 6 Months Ended
Mar. 21, 2017
USD ($)
Jul. 01, 2017
USD ($)
day
$ / shares
shares
Apr. 01, 2017
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Jul. 01, 2017
USD ($)
$ / shares
Jun. 25, 2016
USD ($)
Jun. 30, 2017
$ / shares
Dec. 31, 2016
USD ($)
Sep. 28, 2016
USD ($)
Sep. 14, 2016
USD ($)
Apr. 14, 2015
USD ($)
Jun. 16, 2014
USD ($)
Feb. 26, 2014
USD ($)
Aug. 15, 2012
USD ($)
Debt Instrument [Line Items]                          
Repayments of Long-Term Debt       $ 42,000,000 $ 0                
2.125% Convertible Senior Notes Due 2026 [Member]                          
Debt Instrument [Line Items]                          
Principal   $ 805,000,000   $ 805,000,000     $ 805,000,000 $ 105,000,000 $ 700,000,000        
Debt Conversion, Converted Instrument, Shares Issued | shares   125.0031                      
Debt Instrument, Convertible, Conversion Price | $ / shares   $ 8.00   $ 8.00                  
Debt Issuance Cost, Gross, Noncurrent             15,000,000            
Equity issuance costs             9,000,000            
Debt Instrument, Convertible, Remaining Life       111 months                  
Share price (in usd per share) | $ / shares           $ 12.48              
Debt Instrument, Interest Rate, Effective Percentage   8.00%   8.00%                  
Debt Instrument, Convertible, If-converted Value in Excess of Principal   $ 451,000,000                      
Debt Instrument, Interest Rate, Stated Percentage   2.125%   2.125%                  
2.125% Convertible Senior Notes Due 2026 [Member] | Debt Instrument, Redemption, Period One [Member]                          
Debt Instrument [Line Items]                          
Debt Instrument, Convertible, Threshold Trading Days | day   20                      
Debt Instrument, Convertible, Threshold Consecutive Trading Days | day   30                      
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger   130.00%                      
2.125% Convertible Senior Notes Due 2026 [Member] | Debt Instrument, Redemption, Period Two [Member]                          
Debt Instrument [Line Items]                          
Debt Instrument, Convertible, Threshold Consecutive Trading Days | day   10                      
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger   98.00%                      
Debt Instrument, Convertible, Conversion Period After Threshold Period Days | day   5                      
6.75% Senior Notes due 2019 [Member]                          
Debt Instrument [Line Items]                          
Principal                       $ 600,000,000  
Outstanding Aggregate Principal Amount   $ 191,000,000   $ 191,000,000                  
Debt Instrument, Interest Rate, Stated Percentage   6.75%   6.75%                  
Extinguishment of Debt, Amount     $ 5,000,000                    
7.50% Senior Notes due 2022 [Member]                          
Debt Instrument [Line Items]                          
Principal                         $ 500,000,000
Outstanding Aggregate Principal Amount   $ 347,000,000   $ 347,000,000                  
Debt Instrument, Interest Rate, Stated Percentage   7.50%   7.50%                  
Extinguishment of Debt, Amount     3,000,000                    
7.00% Senior Notes due 2024 [Member]                          
Debt Instrument [Line Items]                          
Principal                     $ 500,000,000    
Outstanding Aggregate Principal Amount   $ 350,000,000   $ 350,000,000                  
Debt Instrument, Interest Rate, Stated Percentage   7.00%   7.00%                  
Repayments of Long-Term Debt   $ 42,000,000                      
Extinguishment of Debt, Amount   40,000,000 $ 26,000,000                    
Revolving Credit Facility [Member]                          
Debt Instrument [Line Items]                          
Secured revolving line of credit, maximum borrowing capacity $ 500,000,000                        
Secured revolving line of credit, additional borrowing capacity 200,000,000                        
Secured revolving line of credit, outstanding balance   $ 42,000,000   $ 42,000,000     $ 0            
Secured revolving line of credit, interest rate   4.75%   4.75%                  
Letters of credit outstanding, amount   $ 19,000,000   $ 19,000,000                  
Secured revolving line of credit, remaining borrowing capacity   $ 249,000,000   $ 249,000,000                  
Debt Instrument, Repayment Period       90 days                  
Letter of Credit [Member]                          
Debt Instrument [Line Items]                          
Secured revolving line of credit, maximum borrowing capacity $ 45,000,000                 $ 75,000,000      
Maximum [Member] | Revolving Credit Facility [Member]                          
Debt Instrument [Line Items]                          
Debt Instrument, Percentage of Eligible Accounts Receivable 85.00%                        
Debt Instrument, Percentage of Certain Qualified Eligible Accounts Receivable 90.00%