Mortgage Banking Activities, Loan Servicing Portfolio (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	$ 173,286,000	$ 155,740,000	$ 153,333,000	$ 140,863,000	$ 132,889,000	$ 100,812,000
Outstanding principal of loans serviced for others	15,499,653,000
Weighted average prepayment rate (in hundredths)	9.37%
Increase in Fair Value Of Mortgage Servicing Rights Due To 50 Basis Point Increase In Mortgage Interest Rates	3,200,000
Decrease in Fair Value Of Mortgage Servicing Rights Due To 50 Basis Point Decrease In Mortgage Interest Rates	5,400,000
Interest Rate Range Less than 4.00% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	66,895,000
Outstanding principal of loans serviced for others	5,988,358,000
Weighted average prepayment rate (in hundredths)	7.10%
Interest Rate Range 4.00% to 4.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	77,537,000
Outstanding principal of loans serviced for others	6,410,710,000
Weighted average prepayment rate (in hundredths)	8.06%
Interest Rate Range 5.00% to 5.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	23,011,000
Outstanding principal of loans serviced for others	2,090,157,000
Weighted average prepayment rate (in hundredths)	11.63%
Interest Rate Range Greater than 5.99% [Member]
Stratification of Mortgage Loan Servicing Portfolio [Line Items]
Fair value	5,843,000
Outstanding principal of loans serviced for others	$ 1,010,428,000
Weighted average prepayment rate (in hundredths)	26.41%