Accumulated Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Loss After Tax (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance			$ (38,252)
Total other comprehensive income	3,367	8,474	7,955	11,757
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(30,297)		(30,297)
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	7,123		14,339
Amounts reclassified from other comprehensive income	(4)		1
Total other comprehensive income	7,119		14,340
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(6,515)	(13,634)	(6,515)	(13,634)
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	164		306
Amounts reclassified from other comprehensive income	(64)		(179)
Total other comprehensive income	100		127
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(679)	(779)	(679)	(779)
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	(4,862)		(8,524)
Amounts reclassified from other comprehensive income	973		1,938
Total other comprehensive income	(3,889)		(6,586)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(12,857)	(8,968)	(12,857)	(8,968)
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	37		74
Total other comprehensive income	37		74
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(10,246)	(10,283)	(10,246)	(10,283)
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	2,425		6,121
Amounts reclassified from other comprehensive income	942		1,834
Total other comprehensive income	3,367		7,955
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (30,297)	$ (33,664)	$ (30,297)	$ (33,664)