Description of Business and Significant Accounting Policies - Out of Period Adjustments (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||
---|---|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
Error Corrections and Prior Period Adjustments Restatement [Line Items] | |||||
Income tax benefit | $ (55) | $ 48 | $ (98) | ||
Misapplication of Accounting Guidance Related to Recognition of Income Tax Expense [Member] | |||||
Error Corrections and Prior Period Adjustments Restatement [Line Items] | |||||
Income tax benefit | $ 5 | $ 15 |