Accumulated Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Loss After Tax (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)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			$ (42,495)
Total other comprehensive (loss) income	$ (3,598)	$ 3,367	(5,765)	$ 7,955
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(48,260)		(48,260)
Unrealized Gains and (Losses) on Available for Sale (AFS) Securities
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	637		(1,890)
Other comprehensive income (loss) before reclassifications	(5,845)		(1,909)
Amounts reclassified from other comprehensive income (loss)	55		(1,354)
Total other comprehensive (loss) income	(5,790)		(3,263)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(5,153)		(5,153)
Non-credit Impairment Losses on AFS Securities
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(360)		145
Other comprehensive income (loss) before reclassifications	(31)		(452)
Amounts reclassified from other comprehensive income (loss)	(20)		(104)
Total other comprehensive (loss) income	(51)		(556)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(411)		(411)
Unrealized Gains and (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(18,840)		(14,532)
Other comprehensive income (loss) before reclassifications	1,131		(4,128)
Amounts reclassified from other comprehensive income (loss)	991		1,942
Total other comprehensive (loss) income	2,122		(2,186)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(16,718)		(16,718)
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(44,662)		(42,495)
Other comprehensive income (loss) before reclassifications	(4,745)		(6,489)
Amounts reclassified from other comprehensive income (loss)	1,147		724
Total other comprehensive (loss) income	(3,598)		(5,765)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(48,260)		(48,260)
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(26,099)		(26,218)
Other comprehensive income (loss) before reclassifications	0		0
Amounts reclassified from other comprehensive income (loss)	121		240
Total other comprehensive (loss) income	121		240
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (25,978)		$ (25,978)