Other Intangible Assets and Liabilities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Amortized intangible assets, gross carrying amount	$ 652		$ 647
Amortized intangible assets, accumulated amortization	262		253
Amortized intangible liabilities, gross carrying amount	1,403		1,403
Amortized intangible liabilities, accumulated amortization	955		$ 932
Amortization of Intangible Assets	9	$ 9
Amortization of Intangible Liabilities	23	$ 24
Finite-Lived Intangible Assets and Liabilities, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Amortization of intangible assets, Remainder of 2018	25
Amortization of intangible liabilities, Remainder of 2018	67
Amortization of intangible assets, 2019	33
Amortization of intangible liabilities, 2019	27
Amortization of intangible assets, 2020	33
Amortization of intangible liabilities, 2020	26
Amortization of intangible assets, 2021	31
Amortization of intangible liabilities, 2021	24
Amortization of intangible assets, 2022	31
Amortization of intangible liabilities, 2022	$ 23