Goodwill and Other Intangible Assets (Intangible Assets) - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Goodwill	$ 1,534	$ 1,430
Customer Relations And Supply Agreements [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Remaining weighted-average life	11 years
Favorable leasehold arrangements, net [Member] | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Remaining weighted-average life	13 years
Noncompete Agreements | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Remaining weighted-average life	10 years
Deferred Loan Origination Costs | Weighted Average [Member]
Finite Lived Intangible Assets [Line Items]
Remaining weighted-average life	4 years