Mortgage Banking Activities, Mortgage Servicing Rights (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2012		Jun. 30, 2011	Jun. 30, 2012		Jun. 30, 2011	Dec. 31, 2011
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced	96,772,000		96,578,000	96,772,000		96,578,000	95,841,000
Outstanding principal balance of residential mortgage loans serviced for others	$ 11,564,643		$ 11,283,442	$ 11,564,643		$ 11,283,442	$ 11,300,986
Weighted average interest rate (in hundredths)	4.99%					5.36%	5.19%
Remaining term (in months)	289		291	289		291	290
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	98,138		120,345	86,783		115,723	115,723
Additions, net	9,275		5,798	17,647		10,767
Change in fair value due to loan runoff	(4,180)		(3,458)	(8,324)		(6,934)
Change in fair value due to market changes	(11,450)		(13,493)	(4,323)		(10,364)
Ending balance	91,783	[1]	109,192	91,783	[1]	109,192	86,783
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)				10.33%		10.40%	10.34%
Prepayment rate - estimated based upon loan interest rate, original term and loan type, minimum (in hundredths)				11.44%		10.26%	10.88%
Prepayment rate - estimated based upon loan interest rate, original term and loan type, maximum (in hundredths)				53.10%		38.37%	49.68%
Loan servicing costs - annually per loan based upon loan type, minimum (in dollars per loan)				55		55	55
Loan servicing costs - annually per loan based upon loan type, maximum (in dollars per loan)				105		105	105
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life (in hundredths)				0.97%		2.02%	1.21%
Purchased [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	21,204		38,343	18,903		37,900	37,900
Additions, net	0		0	0		0
Change in fair value due to loan runoff	(950)		(1,218)	(1,960)		(2,551)
Change in fair value due to market changes	(3,893)		(4,259)	(582)		(2,483)
Ending balance	16,361		32,866	16,361		32,866
Originated [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	76,934		82,002	67,880		77,823	77,823
Additions, net	9,275		5,798	17,647		10,767
Change in fair value due to loan runoff	(3,230)		(2,240)	(6,364)		(4,383)
Change in fair value due to market changes	(7,557)		(9,234)	(3,741)		(7,881)
Ending balance	$ 75,422		$ 76,326	$ 75,422		$ 76,326

[1] A reconciliation of the beginning and ending fair value of mortgage servicing rights and disclosures of significant assumptions used to determine fair value are presented in Note 5, Mortgage Banking Activities.