Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net operating revenues	$ 1,267,401	$ 1,077,014	$ 3,816,575	$ 3,270,996
Provision for bad debts		169	(373)	914
Changes in accounts receivable			23,495	(143,308)
Accounts receivable					$ 691,732
Allowance for doubtful accounts					0
Accounts receivable	$ 746,816		$ 746,816		691,732
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net operating revenues		1,097,166		3,329,202
Provision for bad debts		20,321		59,120
Changes in accounts receivable				(201,514)
Accounts receivable					767,276
Allowance for doubtful accounts					75,544
Accounts receivable					691,732
Accounting Standards Update 2014-09 | Adoption Impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net operating revenues		(20,152)		(58,206)
Provision for bad debts		$ (20,152)		(58,206)
Changes in accounts receivable				$ 58,206
Accounts receivable					(75,544)
Allowance for doubtful accounts					(75,544)
Accounts receivable					$ 0