Business and Significant Accounting Policies (Details) - Intangible Assets Subject to Amortization - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-lived Intangible Assets [Roll Forward]
Gross cost	$ 116,767	$ 118,003
Additions due to acquisitions	1,600,190	5,927
Intangibles fully amortized	(4,227)	(287)
Reclassified as held-for-sale	(250,472)
Foreign currency translation impact	20,724	(6,876)
Gross cost	1,482,982	116,767
Accumulated amortization	(190,960)	(39,966)
Finite-lived intangible assets, net	1,292,022	76,801
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost	63,369	62,860
Additions due to acquisitions	1,253,312	3,677
Intangibles fully amortized	0	0
Reclassified as held-for-sale	(140,156)
Foreign currency translation impact	23,791	(3,168)
Gross cost	1,200,316	63,369
Accumulated amortization	(92,983)	(16,744)
Finite-lived intangible assets, net	1,107,333	46,625
Software
Finite-lived Intangible Assets [Roll Forward]
Gross cost	16,025	16,219
Additions due to acquisitions	180,787	0
Intangibles fully amortized	0	(125)
Reclassified as held-for-sale	(69,012)
Foreign currency translation impact	(4,376)	(69)
Gross cost	123,424	16,025
Accumulated amortization	(26,344)	(8,904)
Finite-lived intangible assets, net	97,080	7,121
Content
Finite-lived Intangible Assets [Roll Forward]
Gross cost	3,728	5,450
Additions due to acquisitions	141,707	1,948
Intangibles fully amortized	(4,227)	(162)
Reclassified as held-for-sale	(38,593)
Foreign currency translation impact	1,698	(3,508)
Gross cost	104,313	3,728
Accumulated amortization	(47,475)	(2,033)
Finite-lived intangible assets, net	56,838	1,695
Other
Finite-lived Intangible Assets [Roll Forward]
Gross cost	33,645	33,474
Additions due to acquisitions	24,384	302
Intangibles fully amortized	0	0
Reclassified as held-for-sale	(2,711)
Foreign currency translation impact	(389)	(131)
Gross cost	54,929	33,645
Accumulated amortization	(24,158)	(12,285)
Finite-lived intangible assets, net	$ 30,771	$ 21,360