Certain Transfers of Financial Assets (Details 2) (Residential mortgage, USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Assumptions and estimates in determining the impairment of capitalized MSRs    
Servicing Asset at Fair Value, Amount $ 63,977 $ 53,742
Composition of Loans Serviced for Others 100.00% 100.00%
Weighted average remaining term (years) 26 years 26 years
Prepayment speed 9.24% 7.33%
Decline in fair value due to a 10% adverse change (2,149) (1,449)
Decline in fair value due to a 20% adverse change (4,149) (2,830)
Decline in fair value due to a 10% adverse change (2,231) (2,012)
Decline in fair value due to a 20% adverse change $ (4,298) $ (3,880)
Weighted Average
    
Assumptions and estimates in determining the impairment of capitalized MSRs    
Weighted average discount rate 9.73% 10.14%
Fixed-rate mortgage loans
    
Assumptions and estimates in determining the impairment of capitalized MSRs    
Composition of Loans Serviced for Others 99.40% 99.60%
Adjustable-rate mortgage loans
    
Assumptions and estimates in determining the impairment of capitalized MSRs    
Composition of Loans Serviced for Others 0.60% 0.40%