Accumulated Other Comprehensive Income (Loss) - Changes, net of tax, in Accumulated Other Comprehensive income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, January 1, 2015	$ (15,206)
Other comprehensive income (loss) before reclassifications	(24,935)
Reclassifications from accumulated other comprehensive income	34,595
Current period other comprehensive income (loss)	9,660	$ (25,246)	$ 9,094
Balance, December 31, 2015	(5,546)	(15,206)
Unrealized Gain (Loss) on Securities
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, January 1, 2015	(14,821)
Other comprehensive income (loss) before reclassifications	(24,927)
Reclassifications from accumulated other comprehensive income	34,595
Current period other comprehensive income (loss)	9,668
Balance, December 31, 2015	(5,153)	(14,821)
Cumulative Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, January 1, 2015	(385)
Other comprehensive income (loss) before reclassifications	(8)
Reclassifications from accumulated other comprehensive income	0
Current period other comprehensive income (loss)	(8)
Balance, December 31, 2015	$ (393)	$ (385)