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
Mar. 21, 2017
USD ($)
Apr. 01, 2017
USD ($)
day
$ / shares
shares
Mar. 31, 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 ($)
2.125% Convertible Senior Notes Due 2026 [Member]                    
Debt Instrument [Line Items]                    
Principal   $ 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                
Debt Issuance Cost, Gross, Noncurrent       15,000,000            
Equity issuance costs       9,000,000            
Debt Instrument, Convertible, Remaining Life   114 months                
Share price (in usd per share) | $ / shares     $ 14.55              
Debt Instrument, Interest Rate, Effective Percentage   8.00%                
Debt Instrument, Convertible, If-converted Value in Excess of Principal   $ 659,000,000                
Debt Instrument, Interest Rate, Stated Percentage   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   30 days                
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   10 days                
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                
Debt Instrument, Interest Rate, Stated Percentage   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                
Debt Instrument, Interest Rate, Stated Percentage   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   $ 390,000,000                
Debt Instrument, Interest Rate, Stated Percentage   7.00%                
Extinguishment of Debt, Amount   $ 26,000,000                
Revolving Credit Facility [Member]                    
Debt Instrument [Line Items]                    
Line of Credit Facility, Maximum Borrowing Capacity $ 500,000,000                  
Line of Credit Facility, Additional Borrowing Capacity 200,000,000                  
Line of Credit, Current   0   $ 0            
Letters of Credit Outstanding, Amount   19,000,000                
Line of Credit Facility, Remaining Borrowing Capacity   $ 209,000,000                
Debt Instrument, Repayment Period   90 days                
Letter of Credit [Member]                    
Debt Instrument [Line Items]                    
Line of Credit Facility, 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%