Stockholders' Equity - Components of Accumulated Other Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), Beginning balance	$ (35,379)	$ (22,925)
Other comprehensive income before income taxes:
Net change in unrealized (loss) gain	4,514	(12,438)
Transfer of net unrealized gain from AFS to HTM, net of cumulative tax effect
Reclassification of net (gains) losses realized and included in earnings	53	1,929
Amortization/accretion of unrealized net gain/loss on securities transferred to HTM	665	(2,984)
Income tax (benefit) expense	1,842	(4,940)
Accumulated other comprehensive income (loss), Ending balance	(31,989)	(31,478)
Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), Beginning balance	8,263	38,854
Other comprehensive income before income taxes:
Net change in unrealized (loss) gain	4,514	(12,434)
Transfer of net unrealized gain from AFS to HTM, net of cumulative tax effect
Reclassification of net (gains) losses realized and included in earnings
Amortization/accretion of unrealized net gain/loss on securities transferred to HTM
Income tax (benefit) expense	1,598	(4,586)
Accumulated other comprehensive income (loss), Ending balance	11,179	31,006
Held to Maturity Securities Transferred from AFS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), Beginning balance	(21,189)	19,090
Other comprehensive income before income taxes:
Net change in unrealized (loss) gain
Transfer of net unrealized gain from AFS to HTM, net of cumulative tax effect
Reclassification of net (gains) losses realized and included in earnings
Amortization/accretion of unrealized net gain/loss on securities transferred to HTM	665	(2,984)
Income tax (benefit) expense	225	(1,078)
Accumulated other comprehensive income (loss), Ending balance	(20,749)	17,184
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), Beginning balance	(22,453)	(80,688)
Other comprehensive income before income taxes:
Net change in unrealized (loss) gain
Transfer of net unrealized gain from AFS to HTM, net of cumulative tax effect
Reclassification of net (gains) losses realized and included in earnings	53	1,754
Amortization/accretion of unrealized net gain/loss on securities transferred to HTM
Income tax (benefit) expense	19	657
Accumulated other comprehensive income (loss), Ending balance	(22,419)	(79,591)
Loss on Effective Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), Beginning balance		(181)
Other comprehensive income before income taxes:
Net change in unrealized (loss) gain		(4)
Transfer of net unrealized gain from AFS to HTM, net of cumulative tax effect
Reclassification of net (gains) losses realized and included in earnings		175
Amortization/accretion of unrealized net gain/loss on securities transferred to HTM
Income tax (benefit) expense		67
Accumulated other comprehensive income (loss), Ending balance		$ (77)