Other Comprehensive Income (Loss) and Related Tax Effects (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 4,179,536	$ 4,205,515	$ 4,155,474	$ 4,177,385
Cumulative effect of accounting changes as of January 1, 2018					$ 25,125
Balance, January 1					4,202,510
Other comprehensive income (loss) before reclassifications			6,166	(34,321)
Amounts reclassified to net income			(566)	(3)
Total other comprehensive income (loss), net of tax	4,751	(43,183)	5,600	(35,123)
Ending balance	4,242,951	4,244,252	4,242,951	4,244,252
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(124,251)	(111,413)	(125,100)	(130,154)
Cumulative effect of accounting changes as of January 1, 2018					10,467
Balance, January 1					(119,687)
Total other comprehensive income (loss), net of tax			5,600	(34,324)
Ending balance	(119,500)	(154,011)	(119,500)	(154,011)
Cumulative Foreign Currency Translation Losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(121,693)	(119,430)
Cumulative effect of accounting changes as of January 1, 2018					0
Balance, January 1					(119,430)
Other comprehensive income (loss) before reclassifications			3,807	(34,336)
Amounts reclassified to net income			0	0
Total other comprehensive income (loss), net of tax			3,807	(34,336)
Ending balance	(117,886)	(153,766)	(117,886)	(153,766)
Unrealized Gain (Loss) On Available-For-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(1,574)	(10,801)
Cumulative effect of accounting changes as of January 1, 2018					10,467
Balance, January 1					(334)
Other comprehensive income (loss) before reclassifications			3,291	256
Amounts reclassified to net income			(566)	(3)
Total other comprehensive income (loss), net of tax			2,725	253
Ending balance	1,151	(81)	1,151	(81)
Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(1,833)	77
Cumulative effect of accounting changes as of January 1, 2018					0
Balance, January 1					$ 77
Other comprehensive income (loss) before reclassifications			(932)	(241)
Amounts reclassified to net income			0	0
Total other comprehensive income (loss), net of tax			(932)	(241)
Ending balance	$ (2,765)	$ (164)	$ (2,765)	$ (164)