New Accounting Principles and Recent Accounting Pronouncements Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 618,100	$ 590,938		$ 590,938		$ 0
Operating lease liabilities, current	155,500	128,635		128,635		$ 0
Non-current lease liabilities	468,400
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to retained earnings	$ 116,800	$ 0	$ 0	$ 116,768	$ 0