Goodwill And Other Intangible Assets - Changes in carrying amounts of intangible assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-lived Intangible Assets [Roll Forward]
Balance as of December 31, 2017	$ 858,565
Amortization	(41,907)
Foreign currency translation adjustment	199
Balance as of March 31, 2018	816,857
Indefinite-lived Intangible Assets [Roll Forward]
Balance at December 31, 2017	755,100
Balance as of March 31, 2018 and December 31, 2017	755,100
Goodwill [Roll Forward]
Gross balance as of December 31, 2017		$ 3,609,988
Accumulated impairment losses at December 31, 2017		(381,000)
Balance at December 31, 2017	3,228,988
Foreign currency translation adjustment	250
Balance as of March 31, 2018	3,229,238
Total goodwill and other intangible assets	$ 4,801,195	$ 4,842,653