Segment Reporting Segment Reporting - Condensed Balance Sheet - By Segment (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets	$ 25,151	$ 25,436
Liabilities	21,849	22,139
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Assets	7,399	7,459
Liabilities	11,554	11,780
Intersegment Elimination
Segment Reporting Information [Line Items]
Assets	(3,037)	(3,032)
Liabilities	103	108
Las Vegas, NV [Member] | Operating Segments
Segment Reporting Information [Line Items]
Assets	14,062	14,145
Liabilities	5,196	5,239
Other U.S. [Member] | Operating Segments
Segment Reporting Information [Line Items]
Assets	6,727	6,864
Liabilities	$ 4,996	$ 5,012