Mortgage Banking Activities, Mortgage Servicing Rights (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced for others	114,493	106,137	104,115	114,493	104,115
Outstanding principal balance of residential mortgage loans serviced for others	$ 15,499,653,000	$ 13,718,942,000	$ 13,298,479,000	$ 15,499,653,000	$ 13,298,479,000
Weighted average interest rate (in hundredths)	4.33%	4.40%	4.42%	4.33%	4.42%
Remaining term (in months)	295 months	292 months	292 months
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	155,740,000	140,863,000	132,889,000	153,333,000	100,812,000
Additions, net	17,367,000		13,225,000	39,183,000	39,157,000
Change in fair value due to loan runoff	(5,102,000)		(4,905,000)	(13,606,000)	(15,733,000)
Change in fair value due to market changes	5,281,000		(346,000)	(5,624,000)	16,627,000
Ending balance	173,286,000	153,333,000	140,863,000	173,286,000	140,863,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)	10.17%	10.21%	10.23%
Loan servicing costs - annually per loan based upon loan type, performing, minimum (in dollars per loan)	60	60	58
Loan servicing costs - annually per loan based upon loan type, performing, maximum (in dollars per loan)	105	105	105
Loan servicing costs - annually per loan based upon loan type, delinquent, minimum (in dollars per loan)	150	150	135
Loan servicing costs - annually per loan based upon loan type, delinquent, maximum (in dollars per loan)	500	500	500
Loan servicing costs - annually per loan based upon loan type, foreclosure, minimum (in dollars per loan)	1,000	1,000	875
Loan servicing costs - annually per loan based upon loan type, foreclosure, maximum (in dollars per loan)	4,250	4,250	4,250
Escrow earnings rate - indexed to rates paid on deposit accounts with comparable average life (in hundredths)	1.95%	1.80%	1.54%
Purchased [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	13,082,000		15,582,000	15,935,000	12,976,000
Additions, net	0		0	0	0
Change in fair value due to loan runoff	(624,000)		(693,000)	(1,737,000)	(2,504,000)
Change in fair value due to market changes	821,000		(76,000)	(919,000)	4,341,000
Ending balance	13,279,000		14,813,000	13,279,000	14,813,000
Originated [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	142,658,000		117,307,000	137,398,000	87,836,000
Additions, net	17,367,000		13,225,000	39,183,000	39,157,000
Change in fair value due to loan runoff	(4,478,000)		(4,212,000)	(11,869,000)	(13,229,000)
Change in fair value due to market changes	4,460,000		(270,000)	(4,705,000)	12,286,000
Ending balance	$ 160,007,000		$ 126,050,000	$ 160,007,000	$ 126,050,000