Accumulated Other Comprehensive Income - Summary of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		$ 366,028
Reclassification for gains included in net income	$ (6)	(14)	$ (4)
Balance at end of period	486,770	486,770	343,399
Unrealized Gain (Loss) on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		508	1,397
Current year changes		(131)	(638)
Balance at end of period	377	377	759
Unrealized Gain (Loss) on Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		5,590	(1,691)
Reclassification for gains included in net income		(14)	(4)
Current year changes		(2,881)	5,059
Balance at end of period	2,695	2,695	3,364
Accumulated Other Comprehensive Income, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at beginning of period		6,098	(294)
Reclassification for gains included in net income		(14)	(4)
Current year changes		(3,012)	4,421
Balance at end of period	$ 3,072	$ 3,072	$ 4,123