Mortgage Banking (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Mortgage servicing rights [Abstract]
Balance at beginning of period	$ 64,358	$ 67,834
Origination of servicing assets	8,157	5,179
Change in fair value [Abstract]
Due to market changes	3,708	(3,761)
Due to runoff	(4,801)	(4,203)
Balance at end of period	71,422	65,049
Residential mortgage loans sold	579,900	397,900
Gains on sales of residential mortgage loans, before tax	$ 8,800	4,600
Period of putback response	60 days
Mortgage Loans on Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 5,732,187		$ 5,636,249
Schedule of changes in the reserve for mortgage loan [Abstract]
Balance at beginning of period	1,170	1,050
Provision for putback expenses	105	300
Losses	123	(403)
Balance at end of period	1,401	947
Mortgage loan servicing putback expenses	105	$ 300
Federal National Mortgage Association [Member]
Mortgage Loans on Real Estate [Line Items]
Total mortgage loans sold and serviced for others	3,642,950		3,579,987
Government National Mortgage Association [Member]
Mortgage Loans on Real Estate [Line Items]
Total mortgage loans sold and serviced for others	1,971,315		1,948,565
Federal Home Loan Mortgage Corporation [Member]
Mortgage Loans on Real Estate [Line Items]
Total mortgage loans sold and serviced for others	71,890		80,551
Other [Member]
Mortgage Loans on Real Estate [Line Items]
Total mortgage loans sold and serviced for others	$ 46,032		$ 27,146