Accumulated Other Comprehensive Income - Changes, net of tax, in Accumulated other comprehensive income are as follows (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	$ 357,518
Current period other comprehensive income (loss)	8,674
Balance at end of period	331,547
Unrealized Gains on Securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(14,821)
Other comprehensive loss before reclassifications	(2,807)
Reclassifications from accumulated other comprehensive income	11,487
Current period other comprehensive income (loss)	8,680
Balance at end of period	(6,141)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(385)
Other comprehensive loss before reclassifications	(6)
Reclassifications from accumulated other comprehensive income	0
Current period other comprehensive income (loss)	(6)
Balance at end of period	(391)
Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(15,206)
Other comprehensive loss before reclassifications	(2,813)
Reclassifications from accumulated other comprehensive income	11,487
Current period other comprehensive income (loss)	8,674
Balance at end of period	$ (6,532)