Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 2,042,306	$ 1,338,191	$ 1,093,628
Other comprehensive income before reclassifications	34,577	(35,390)	28,996
Amounts reclassified from accumulated other comprehensive income (loss)	1,774	2,645	(9,647)
Total changes in other comprehensive income (loss)	36,351	(32,745)	19,349
Balance	4,435,203	2,042,306	1,338,191
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(21,031)	(7,862)	(2,080)
Other comprehensive income before reclassifications	8,855	(13,169)	(5,782)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Total changes in other comprehensive income (loss)	8,855	(13,169)	(5,782)
Balance	(11,227)	(21,031)	(7,862)
On Available-For-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(594)	(10)	126
Other comprehensive income before reclassifications	58	(584)	(136)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Total changes in other comprehensive income (loss)	58	(584)	(136)
Balance	(536)	(594)	(10)
On Equity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	25,069	17,531	0
Other comprehensive income before reclassifications	0	7,538	17,531
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0
Total changes in other comprehensive income (loss)	0	7,538	17,531
Balance	0	25,069	17,531
On Foreign Currency Forward Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(15,016)	11,514	3,778
Other comprehensive income before reclassifications	25,664	(29,175)	17,383
Amounts reclassified from accumulated other comprehensive income (loss)	1,774	2,645	(9,647)
Total changes in other comprehensive income (loss)	27,438	(26,530)	7,736
Balance	12,422	(15,016)	11,514
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(11,572)	21,173	1,824
Total changes in other comprehensive income (loss)	36,351	(32,745)	19,349
Balance	659	$ (11,572)	$ 21,173
Accounting Standards Update 2014-09
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment for adoption of new accounting guidance	(24,120)
Accounting Standards Update 2014-09 | Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment for adoption of new accounting guidance	949
Accounting Standards Update 2014-09 | On Available-For-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment for adoption of new accounting guidance	0
Accounting Standards Update 2014-09 | On Equity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment for adoption of new accounting guidance	(25,069)
Accounting Standards Update 2014-09 | On Foreign Currency Forward Contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustment for adoption of new accounting guidance	$ 0