Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 104,360	$ 104,449
Accumulated Amortization	(67,629)	(70,280)
Valuation Allowance	(1,759)	(3,046)
Net Intangible Assets	34,972	31,123
Loan servicing rights [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	63,288	63,377
Accumulated Amortization	(39,716)	(43,393)
Valuation Allowance	(1,759)	(3,046)
Net Intangible Assets	21,813	16,938
Core deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	35,194	35,194
Accumulated Amortization	(25,024)	(24,160)
Valuation Allowance
Net Intangible Assets	10,170	11,034
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	5,878	5,878
Accumulated Amortization	(2,889)	(2,727)
Valuation Allowance
Net Intangible Assets	$ 2,989	$ 3,151