Summary of Intangible Asset Account Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Total Intangible Assets [Abstract]
Beginning balance, intangible assets, gross	$ 769,851	$ 669,896
Finite-lived Intangible Assets Acquired	240,600	0
Effect of change in exchange rates	22,979	16,168
Intangible Assets, Gross (Excluding Goodwill)	1,033,430	686,064
Finite-lived intangible liabilities, Gross	(23,900)	0	$ 0	$ 0
Finite-Lived Intangible Liabilities Acquired	(23,900)	0
Finite-Lived Intangible Liabilities, Foreign Currency Translation Gain Loss	$ 0	$ 0