Mortgage Banking Activities, Loan Servicing Portfolio (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	$ 153,333,000		$ 100,812,000	$ 86,783,000	$ 115,723,000
Outstanding principal of loans serviced others	13,718,942,000
Weighted average prepayment rate (in hundredths)	9.34%	[1]
Economic hedge threshold for interest rate sensitivity for mortgage servicing rights and securities held (in basis points)	50
Dollar increase in fair value, net of economic hedge, of mortgage servicing rights due to 50 basis point increase in mortgage interest rates	2,100,000
Dollar decrease in fair value, net of economic hedge, of mortgage servicing rights due to 50 basis point decrease in mortgage interest rates	2,300,000
Interest Rate Range Less than 4.00% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	62,962,000
Outstanding principal of loans serviced others	5,454,084,000
Weighted average prepayment rate (in hundredths)	6.66%	[1]
Interest Rate Range 4.00% to 4.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	55,721,000
Outstanding principal of loans serviced others	4,711,703,000
Weighted average prepayment rate (in hundredths)	7.85%	[1]
Interest Rate Range 5.00% to 5.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	27,446,000
Outstanding principal of loans serviced others	2,350,924,000
Weighted average prepayment rate (in hundredths)	9.93%	[1]
Interest Rate Range Greater than 5.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	7,204,000
Outstanding principal of loans serviced others	$ 1,202,231,000
Weighted average prepayment rate (in hundredths)	26.19%	[1]

[1] Annual prepayment estimates based upon loan interest rate, original term and loan type. Weighted average prepayment rate is determined by weighting the prepayment speed for each loan by its unpaid principal balance.