Accumulated Other Comprehensive Income (Summary of Changes in Accumulated Balances in Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 1,263,168	$ 1,072,098	$ 1,311,192	$ 1,035,744
Other comprehensive income (loss)	(3,194)		(11,532)
Net current period other comprehensive income (loss)	(3,194)	(8,166)	(11,532)	(8,294)
Ending balance	1,176,337	1,084,368	1,176,337	1,084,368
Unrealized Gains (Losses) on Investments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	270		(275)
Other comprehensive income (loss)	8		553
Net current period other comprehensive income (loss)	8		553
Ending balance	278		278
Foreign Currency Translation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(55,070)		(46,187)
Other comprehensive income (loss)	(3,202)		(12,085)
Net current period other comprehensive income (loss)	(3,202)		(12,085)
Ending balance	(58,272)		(58,272)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(54,800)	(46,107)	(46,462)	(45,979)
Net current period other comprehensive income (loss)	(3,194)	(8,166)	(11,532)	(8,294)
Ending balance	$ (57,994)	$ (54,273)	$ (57,994)	$ (54,273)