Goodwill and Intangible Assets - Actual and Estimated Future Amortization Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Actual for the year ended
Amortization of intangibles	$ 386	$ 430	$ 532
Estimated future amounts for the year ended December 31,
2017	245
2018	176
2019	108
2020	57
2021	27
Thereafter	48
Net Carrying Amount	$ 661