Mortgage Banking Activities, Mortgage Servicing Rights (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
Summary of Mortgage Servicing Rights [Abstract]
Number of residential mortgage loans serviced for others	107,660	99,438		106,137
Outstanding principal balance of residential mortgage loans serviced for others	$ 14,045,642,000	$ 12,272,691,000		$ 13,718,942,000
Weighted average interest rate (in hundredths)	4.38%	4.59%		4.40%
Remaining term (in months)	292 months	290 months		292 months
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	153,333,000	100,812,000
Additions, net	8,644,000	11,433,000
Change in fair value due to loan runoff	(3,742,000)	(5,063,000)
Change in fair value due to market changes	(4,461,000)	2,658,000
Ending balance	153,774,000	109,840,000	100,812,000
Servicing Assets at Fair Value, Assumptions Used to Estimate Fair Value [Abstract]
Discount rate - risk-free rate plus a market premium (in hundredths)	10.21%	10.27%	10.21%
Loan servicing costs - annually per loan based upon loan type, performing, minimum (in dollars per loan)	60	55	60
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	135	150
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	875	1,000
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)	1.81%	0.97%	1.80%
Purchased [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	15,935,000	12,976,000
Additions, net	0	0
Change in fair value due to loan runoff	(515,000)	(871,000)
Change in fair value due to market changes	(630,000)	1,098,000
Ending balance	14,790,000	13,203,000
Originated [Member]
Servicing Asset at Fair Value, Amount [Roll Forward]
Beginning balance	137,398,000	87,836,000
Additions, net	8,644,000	11,433,000
Change in fair value due to loan runoff	(3,227,000)	(4,192,000)
Change in fair value due to market changes	(3,831,000)	1,560,000
Ending balance	$ 138,984,000	$ 96,637,000