New Accounting Principles and Recent Accounting Pronouncements (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease assets	$ 618,123
Operating lease liabilities, current	155,534
Non-current lease liabilities	468,400
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment to retained earnings	$ 116,768