Annual report pursuant to Section 13 and 15(d)

Income Taxes (Details) (Summary of Tax Attribute Carryforwards)

v3.6.0.2
Income Taxes (Details) (Summary of Tax Attribute Carryforwards)
$ in Millions
Dec. 31, 2016
USD ($)
US-net operating loss carryovers | Federal  
Tax Attribute Carryforwards [Line Items]  
Operating loss carryforwards, amount $ 6,973
US-net operating loss carryovers | State/Provincial  
Tax Attribute Carryforwards [Line Items]  
Operating loss carryforwards, amount 348
US-credit carryovers | Federal  
Tax Attribute Carryforwards [Line Items]  
Tax credit carryforward, amount 398
US-credit carryovers | State/Provincial  
Tax Attribute Carryforwards [Line Items]  
Tax credit carryforward, amount 209
Canada-net operating loss carryovers | Federal  
Tax Attribute Carryforwards [Line Items]  
Operating loss carryforwards, amount 13
Canada-net operating loss carryovers | State/Provincial  
Tax Attribute Carryforwards [Line Items]  
Operating loss carryforwards, amount 13
Canada-credit carryovers | Federal  
Tax Attribute Carryforwards [Line Items]  
Tax credit carryforward, amount 331
Canada-credit carryovers | State/Provincial  
Tax Attribute Carryforwards [Line Items]  
Tax credit carryforward, amount 39
Barbados-net operating loss carryovers | Federal  
Tax Attribute Carryforwards [Line Items]  
Operating loss carryforwards, amount 29
Other foreign net operating loss carryovers | Federal  
Tax Attribute Carryforwards [Line Items]  
Operating loss carryforwards, amount $ 36