Changes in Accumulated Other Comprehensive Income (Loss) by Component - Changes in Accumulated Other Comprehensive Income (loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ (1,047)	$ (3,598)	$ (122)	$ (8,118)
Other comprehensive (loss) before reclassifications	(3,110)	1,612	(4,035)	7,972
Amounts reclassified from accumulated other comprehensive loss to net income (3)	43	(234)	43	(2,074)
Net current-period other comprehensive (loss)	(3,067)	1,378	(3,992)	5,898
Ending balance	(4,114)	(2,220)	(4,114)	(2,220)
Unrealized Gains (Losses) on Available-for-sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	1,385	(4,030)	1,142	(8,118)
Other comprehensive (loss) before reclassifications	(3,389)	2,666	(3,146)	8,594
Amounts reclassified from accumulated other comprehensive loss to net income (3)	43	(234)	43	(2,074)
Net current-period other comprehensive (loss)	(3,346)	2,432	(3,103)	6,520
Ending balance	(1,961)	(1,598)	(1,961)	(1,598)
Unrealized Gain (Loss) on Cash Flow Hedge
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(2,432)	432	(1,264)	0
Other comprehensive (loss) before reclassifications	279	(1,054)	(889)	(622)
Amounts reclassified from accumulated other comprehensive loss to net income (3)	0	0	0	0
Net current-period other comprehensive (loss)	279	(1,054)	(889)	(622)
Ending balance	$ (2,153)	$ (622)	$ (2,153)	$ (622)