Summary of Significant Accounting Policies Change in Accounting Principle (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Total assets	$ 5,438		$ 4,879
Property and equipment, net	1,442	$ 1,545	1,546
Lease right-of-use assets	533	548	0
Accrued expenses and other current liabilities	219	298	299
Current maturities of long-term debt	11	6	5
Operating lease current liabilities	20	25	0
Long term debt, net		2,286	2,280
Operating lease non-current liabilities	530	528	0
Other noncurrent liabilities	$ 97	111	$ 123
Accounting Standards Update 2016-02 [Member]
Total assets		547
Property and equipment, net		(1)
Lease right-of-use assets		548
Accrued expenses and other current liabilities		(1)
Current maturities of long-term debt		1
Operating lease current liabilities		25
Long term debt, net		6
Operating lease non-current liabilities		528
Other noncurrent liabilities		$ (12)