Mortgage Banking Activities, Mortgage Servicing Rights (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced for others	110,404	106,137	101,498	110,404	101,498
Outstanding principal balance of residential mortgage loans serviced for others	$ 14,626,291,000	$ 13,718,942,000	$ 12,741,651,000	$ 14,626,291,000	$ 12,741,651,000
Weighted average interest rate (in hundredths)	4.36%	4.40%	4.47%	4.36%	4.47%
Remaining term (in months)	293 months	292 months	291 months
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	153,774,000		109,840,000	153,333,000	100,812,000
Additions, net	13,172,000		14,499,000	21,816,000	25,932,000
Change in fair value due to loan runoff	(4,762,000)		(5,765,000)	(8,504,000)	(10,828,000)
Change in fair value due to market changes	(6,444,000)		14,315,000	(10,905,000)	16,973,000
Ending balance	155,740,000	153,333,000	132,889,000	155,740,000	132,889,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)	10.20%	10.21%	10.25%
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)	1.69%	1.80%	1.56%
Purchased [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	14,790,000		13,203,000	15,935,000	12,976,000
Additions, net	0		0	0	0
Change in fair value due to loan runoff	(599,000)		(940,000)	(1,114,000)	(1,811,000)
Change in fair value due to market changes	(1,109,000)		3,319,000	(1,739,000)	4,417,000
Ending balance	13,082,000		15,582,000	13,082,000	15,582,000
Originated [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	138,984,000		96,637,000	137,398,000	87,836,000
Additions, net	13,172,000		14,499,000	21,816,000	25,932,000
Change in fair value due to loan runoff	(4,163,000)		(4,825,000)	(7,390,000)	(9,017,000)
Change in fair value due to market changes	(5,335,000)		10,996,000	(9,166,000)	12,556,000
Ending balance	$ 142,658,000		$ 117,307,000	$ 142,658,000	$ 117,307,000