Revenue (Breakdown of Revenues by Accounting Standards) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	$ 911,402	$ 1,547,141
Revenues under ASC 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	356,883	550,533
Revenues under ASC 840
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	26,228	52,257
Revenues under ASC 815
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total Revenues	$ 528,291	$ 944,351