Accumulated Other Comprehensive Loss (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 184,911,000	$ 181,804,000	$ 267,230,000	$ 265,849,000
Other comprehensive loss before reclassifications			(227,000)	(209,000)
Reclassified gains from accumulated other comprehensive loss			0	195,000
Other comprehensive gain (loss), net of tax:	7,000	195,000	(227,000)	(14,000)
Ending Balance	592,227,000	114,560,000	592,227,000	114,560,000
Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			(173,000)	(347,000)
Other comprehensive loss before reclassifications			(2,000)	(9,000)
Reclassified gains from accumulated other comprehensive loss				195,000
Other comprehensive gain (loss), net of tax:			(2,000)	186,000
Ending Balance	(175,000)	(161,000)	(175,000)	(161,000)
Net Unrealized Losses on Available- for-Sale Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			(395,000)	(4,000)
Other comprehensive loss before reclassifications			(225,000)	(200,000)
Reclassified gains from accumulated other comprehensive loss				0
Other comprehensive gain (loss), net of tax:			(225,000)	(200,000)
Ending Balance	(620,000)	(204,000)	(620,000)	(204,000)
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(802,000)	(560,000)	(568,000)	(351,000)
Other comprehensive gain (loss), net of tax:	7,000	195,000	(227,000)	(14,000)
Ending Balance	$ (795,000)	$ (365,000)	$ (795,000)	$ (365,000)