Mortgage Banking Activities, Loan Servicing Portfolio (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012		Mar. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	$ 91,783	[1]	$ 98,138	$ 86,783	$ 109,192	$ 120,345	$ 115,723
Outstanding principal of loans serviced	11,564,643
Weighted average prepayment rate (in hundredths)	21.50%
Interest Rate Range Less than 4.50% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	56,754
Outstanding principal of loans serviced	5,976,173
Weighted average prepayment rate (in hundredths)	11.44%
Interest Rate Range 4.50% to 5.49% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	28,724
Outstanding principal of loans serviced	3,652,815
Weighted average prepayment rate (in hundredths)	23.88%
Interest Rate Range 5.50% to 6.49% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	5,152
Outstanding principal of loans serviced	1,558,553
Weighted average prepayment rate (in hundredths)	20.00%
Interest Rate Range Greater than 6.49% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	1,153
Outstanding principal of loans serviced	$ 377,102
Weighted average prepayment rate (in hundredths)	46.08%

[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.