Property, Plant, and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Movement in Property, Plant and Equipment [Roll Forward]
Beginning Balance	$ 82,482	$ 52,239
Additions to tangible assets	76,030	68,247
Disposal of tangible assets	(8)	(101)
Depreciation expense	(48,161)	(34,327)
Change in consolidation scope	490	118
Currency translation adjustment	(2,252)	(3,694)
Transfer into service	0	0
Ending Balance	108,581	82,482
Gross book value at end of period	215,892	146,522
Accumulated depreciation and impairment at end of period	(107,311)	(64,040)
Fixtures and Fittings
Movement in Property, Plant and Equipment [Roll Forward]
Beginning Balance	14,343	2,501
Additions to tangible assets	6,188	13,408
Disposal of tangible assets	0	(53)
Depreciation expense	(4,496)	(1,840)
Change in consolidation scope	85	31
Currency translation adjustment	(499)	(488)
Transfer into service	2,544	784
Ending Balance	18,165	14,343
Gross book value at end of period	24,200	15,948
Accumulated depreciation and impairment at end of period	(6,035)	(1,605)
Furniture and Equipment
Movement in Property, Plant and Equipment [Roll Forward]
Beginning Balance	63,533	47,391
Additions to tangible assets	57,866	50,849
Disposal of tangible assets	(8)	(48)
Depreciation expense	(43,665)	(32,487)
Change in consolidation scope	405	87
Currency translation adjustment	(1,665)	(2,936)
Transfer into service	1,283	677
Ending Balance	77,749	63,533
Gross book value at end of period	179,025	125,968
Accumulated depreciation and impairment at end of period	(101,276)	(62,435)
Construction in Progress
Movement in Property, Plant and Equipment [Roll Forward]
Beginning Balance	4,606	2,347
Additions to tangible assets	11,976	3,990
Disposal of tangible assets	0	0
Depreciation expense	0	0
Change in consolidation scope	0	0
Currency translation adjustment	(88)	(270)
Transfer into service	(3,827)	(1,461)
Ending Balance	12,667	4,606
Gross book value at end of period	12,667	4,606
Accumulated depreciation and impairment at end of period	$ 0	$ 0