Accumulated Other Comprehensive Income - Changes, net of tax, in Accumulated other comprehensive income are as follows (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	$ 357,518
Current period other comprehensive income	931
Balance at end of period	351,357
Unrealized Gains on Securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(14,821)
Other comprehensive income (loss) before reclassifications	1,114
Reclassifications from accumulated other comprehensive income	(185)
Current period other comprehensive income	929
Balance at end of period	(13,892)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(385)
Other comprehensive income (loss) before reclassifications	2
Reclassifications from accumulated other comprehensive income	0
Current period other comprehensive income	2
Balance at end of period	(383)
Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period	(15,206)
Other comprehensive income (loss) before reclassifications	1,116
Reclassifications from accumulated other comprehensive income	(185)
Current period other comprehensive income	931
Balance at end of period	$ (14,275)