Comprehensive Income - Changes in Accumulated Other Comprehensive Income, Net of Tax, by Component (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), balance at beginning of period	$ (56,924)
Other comprehensive income (loss) before reclassifications	19,033
Amounts reclassified from accumulated other comprehensive income	(6,150)
Net current period other comprehensive income (loss)	12,883	(974)
Accumulated other comprehensive income (loss), balance at end of period	(44,041)
Unrealized Net Gains (Losses) on Securities Available for Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	(11,874)
Other comprehensive income (loss) before reclassifications	10,550
Amounts reclassified from accumulated other comprehensive income	(6,150)
Net current period other comprehensive income (loss)	4,400
Accumulated other comprehensive income (loss), balance at end of period	(7,474)
Non-Credit Related Loss on Debt Securities not Expected to be Sold [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	(6,192)
Other comprehensive income (loss) before reclassifications	6,192
Amounts reclassified from accumulated other comprehensive income
Net current period other comprehensive income (loss)	6,192
Accumulated other comprehensive income (loss), balance at end of period
Unrealized Losses on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	(6,586)
Other comprehensive income (loss) before reclassifications	2,074
Amounts reclassified from accumulated other comprehensive income
Net current period other comprehensive income (loss)	2,074
Accumulated other comprehensive income (loss), balance at end of period	(4,512)
Unrecognized Pension and Postretirement Obligations [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), balance at beginning of period	(32,272)
Other comprehensive income (loss) before reclassifications	217
Amounts reclassified from accumulated other comprehensive income
Net current period other comprehensive income (loss)	217
Accumulated other comprehensive income (loss), balance at end of period	$ (32,055)