Noninterest Income and Expenses (Details) (USD $)	3 Months Ended							6 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Jun. 30, 2011
Components of other noninterest income
Service charges on deposit accounts	$ 3,644,000					$ 3,700,000		$ 7,171,000	$ 7,130,000
ATM and interchange fees	2,026,000					1,776,000		3,845,000	3,421,000
Other service fees	570,000					437,000		1,173,000	843,000
Mortgage banking service fees	379,000					370,000		751,000	731,000
Change in value of mortgage servicing rights	(464,000)					(162,000)		(833,000)	(222,000)
Total service charges and fees	6,155,000					6,121,000		12,107,000	11,903,000
Gain on sale of loans	1,237,000					495,000		2,887,000	1,220,000
Commissions on sale of non-deposit investment products	842,000					648,000		1,661,000	1,008,000
Increase in cash value of life insurance	450,000					450,000		900,000	900,000
Change in indemnification asset	662,000					144,000		309,000	1,836,000
(Gain) loss on sale of foreclosed assets	304,000					185,000		55,000	(385,000)
Sale of customer checks	93,000					67,000		166,000	126,000
Lease brokerage income	90,000					95,000		148,000	128,000
Gain (loss) on disposal of fixed assets	(153,000)					(6,000)		(388,000)	(15,000)
Commission rebates	(18,000)					(16,000)		(34,000)	(33,000)
Gain on life insurance death benefit	600,000							600,000
Other	315,000					68,000		540,000	143,000
Total other noninterest income	4,422,000					2,130,000		6,735,000	5,698,000
Total noninterest income	$ 10,577,000	$ 8,265,000	$ 10,489,000	$ 8,029,000	$ 14,723,000	$ 8,251,000	$ 9,350,000	$ 18,842,000	$ 17,601,000