Revenue (Breakdown of Revenues by Accounting Standards) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	$ 635,739
Revenues under ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	193,650
Revenues under ASC 840
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	26,029
Revenues under ASC 815
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	$ 416,060