Mortgage Banking Activities, Loan Servicing Portfolio (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	$ 132,889	$ 109,840	$ 100,812	$ 91,783	$ 98,138	$ 86,783
Outstanding principal of loans serviced for others	12,741,651
Weighted average prepayment rate (in hundredths)	11.31%
Increase in Fair Value Of Mortgage Servicing Rights Due To 50 Basis Point Increase In Mortgage Interest Rates	207
Decrease in Fair Value Of Mortgage Servicing Rights Due To 50 Basis Point Decrease In Mortgage Interest Rates	586
Interest Rate Range Less than 4.00% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	57,807
Outstanding principal of loans serviced for others	5,075,651
Weighted average prepayment rate (in hundredths)	7.00%
Interest Rate Range 4.00% to 4.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	41,673
Outstanding principal of loans serviced for others	3,739,420
Weighted average prepayment rate (in hundredths)	8.51%
Interest Rate Range 5.00% to 5.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	26,815
Outstanding principal of loans serviced for others	2,551,306
Weighted average prepayment rate (in hundredths)	12.70%
Interest Rate Range Greater than 5.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	6,594
Outstanding principal of loans serviced for others	$ 1,375,274
Weighted average prepayment rate (in hundredths)	32.30%