Other Comprehensive Income (Loss )- Components of Other Comprehensive Loss, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Foreign currency translation adjustment, before taxes	$ 104	$ (359)	$ (675)	$ (43)
Foreign currency translation adjustment, taxes	0	0	0	0
Foreign currency translation adjustment, net of taxes	104	(359)	(675)	(43)
Unrealized gain on investment, before taxes	(7,670)	5,319	(8,018)	8,928
Unrealized gain on investment, tax (expense) benefit	1,992	(1,404)	2,082	(2,356)
Unrealized gain on investment, net of taxes	(5,678)	3,915	(5,936)	6,572
Change in fair value, before taxes	(2,640)	(759)	(4,912)	(1,006)
Change in fair value, tax (expense) benefit	686	201	1,276	266
Change in fair value, net of taxes	(1,954)	(558)	(3,636)	(740)
Reclassification adjustments into earnings, before taxes	337	(72)	333	(146)
Reclassification adjustments into earnings, tax (expense) benefit	(88)	18	(87)	37
Reclassification adjustments into earnings, net of taxes	249	(54)	246	(109)
Net unrealized gain (loss), before taxes	(2,303)	(831)	(4,579)	(1,152)
Net unrealized gain (loss), tax (expense) benefit	598	219	1,189	303
Net unrealized gain (loss), net of taxes	(1,705)	(612)	(3,390)	(849)
Other comprehensive income (loss), before taxes	(9,869)	4,129	(13,272)	7,733
Other comprehensive income (loss), tax (expense) benefit	2,590	(1,185)	3,271	(2,053)
Accumulated Other Comprehensive (Income) Loss, Current period change	$ (7,279)	$ 2,944	$ (10,001)	$ 5,680