Segment Reporting (Schedule of Revenues by Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 315,560	$ 171,394	$ 314,898	$ 187,537	$ 308,689	$ 91,492	$ 298,665	$ 106,531	$ 989,389	$ 805,377	$ 961,494
Intercompany revenue
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									(9,168)	(8,518)	(14,759)
United States | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									383,918	367,200	463,129
United Kingdom | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									229,586	193,721	257,336
Hong Kong and China | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									223,258	145,885	146,262
Switzerland | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									95,653	50,003	50,134
France | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									52,872	42,980	41,803
Other countries | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									$ 13,270	$ 14,106	$ 17,589