Accumulated Other Comprehensive Income - Changes, net of tax, in Accumulated other comprehensive income are as follows (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	$ 357,518
Current period other comprehensive income	15,117
Balance at end of period	355,856
Unrealized Gains on Securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(14,821)
Other comprehensive income (loss) before reclassifications	3,064
Reclassifications from accumulated other comprehensive income	12,054
Current period other comprehensive income	15,118
Balance at end of period	297
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(385)
Other comprehensive income (loss) before reclassifications	(1)
Reclassifications from accumulated other comprehensive income	0
Current period other comprehensive income	(1)
Balance at end of period	(386)
Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(15,206)
Other comprehensive income (loss) before reclassifications	3,063
Reclassifications from accumulated other comprehensive income	12,054
Current period other comprehensive income	15,117
Balance at end of period	$ (89)