Summary of Significant Accounting Policies - Reconciliation of Amounts Previously Reported and Resulting Impacts from Adoption of New Revenue Recognition Guidance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross revenues		$ 6,070,160	$ 4,345,797
Promotional allowances		0	0
Operating revenues	$ 6,717,660	6,070,160	4,345,797
Operating expenses	5,982,116	5,014,595	3,824,135
Operating income	$ 735,544	1,055,565	521,662
As Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross revenues		6,768,246	4,836,355
Promotional allowances		(461,878)	(370,058)
Operating revenues		6,306,368	4,466,297
Operating expenses		5,250,803	3,944,635
Operating income		1,055,565	521,662
Accounting Standards Update 2014-09 | Adoption of ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Gross revenues		(698,086)	(490,558)
Promotional allowances		461,878	370,058
Operating revenues		(236,208)	(120,500)
Operating expenses		(236,208)	(120,500)
Operating income		$ 0	$ 0