Accumulated Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Loss After Tax (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			$ (38,252)
Total other comprehensive income	1,910	466	9,865	12,223
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(28,387)		(28,387)
Unrealized Gains and Losses on Available for Sale (AFS) Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			(20,855)
Other comprehensive income before reclassifications	(488)		13,851
Amounts reclassified from other comprehensive income	(60)		(59)
Total other comprehensive income	(548)		13,792
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(7,063)	(6,515)	(7,063)	(6,515)
Non-Credit Impairment Losses on AFS Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			(806)
Other comprehensive income before reclassifications	313		619
Amounts reclassified from other comprehensive income	(115)		(294)
Total other comprehensive income	198		325
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(481)	(679)	(481)	(679)
Unrealized Gains and Losses on Derivatives [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			(6,271)
Other comprehensive income before reclassifications	1,251		(7,273)
Amounts reclassified from other comprehensive income	973		2,911
Total other comprehensive income	2,224		(4,362)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(10,633)	(12,857)	(10,633)	(12,857)
Defined Benefit Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			(10,320)
Other comprehensive income before reclassifications	0		0
Amounts reclassified from other comprehensive income	36		110
Total other comprehensive income	36		110
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(10,210)	(10,246)	(10,210)	(10,246)
Total Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			(38,252)
Other comprehensive income before reclassifications	1,076		7,197
Amounts reclassified from other comprehensive income	834		2,668
Total other comprehensive income	1,910		9,865
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (28,387)	$ (30,297)	$ (28,387)	$ (30,297)