Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Cash distributions declared and paid	$ 2,500	$ 4,000	$ 3,500
Revenues earned for services provided to related parties	146	178	148
Expenditures to related parties	286	298	297
Parent Company
Related Party Transaction [Line Items]
Cash distributions declared and paid	2,500	4,000	3,500
Tax refund from parent company	235	167	104
Tax payments to parent company	893	1,285	$ 1,253
Tax payable to parent company	$ 109
Refund receivable from parent company		$ 109