Allowance for Credit Losses (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2011
Allowance for Loan Losses:
Beginning balance	$ 73,033,000
Charge-offs	19,605,000
Recoveries	3,305,000
Provision	17,141,000
Ending balance	73,874,000
Ending Balance: individually evaluated for impairment	11,158,000
Ending Balance: collectively evaluated for impairment	62,716,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	6,240,213,000
Ending balance: individually evaluated for impairment	96,770,000
Ending balance: collectively evaluated for impairment	6,104,489,000
Ending Balance: loans acquired with deteriorated credit quality	38,954,000
Owner-occupied [Member]
Allowance for Loan Losses:
Beginning balance	3,116,000
Charge-offs	1,230,000
Recoveries	2,000
Provision	1,782,000
Ending balance	3,670,000
Ending Balance: individually evaluated for impairment	269,000
Ending Balance: collectively evaluated for impairment	3,401,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	743,502,000
Ending balance: individually evaluated for impairment	2,321,000
Ending balance: collectively evaluated for impairment	738,596,000
Ending Balance: loans acquired with deteriorated credit quality	2,585,000
Nonowner-occupied [Member]
Allowance for Loan Losses:
Beginning balance	12,456,000
Charge-offs	897,000
Recoveries	639,000
Provision	(551,000)
Ending balance	11,647,000
Ending Balance: individually evaluated for impairment	596,000
Ending Balance: collectively evaluated for impairment	11,051,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	1,553,259,000
Ending balance: individually evaluated for impairment	29,794,000
Ending balance: collectively evaluated for impairment	1,514,173,000
Ending Balance: loans acquired with deteriorated credit quality	9,292,000
Other commercial [Member]
Allowance for Loan Losses:
Beginning balance	21,918,000
Charge-offs	2,765,000
Recoveries	1,924,000
Provision	(274,000)
Ending balance	20,803,000
Ending Balance: individually evaluated for impairment	5,888,000
Ending Balance: collectively evaluated for impairment	14,915,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	1,212,205,000
Ending balance: individually evaluated for impairment	25,532,000
Ending balance: collectively evaluated for impairment	1,184,565,000
Ending Balance: loans acquired with deteriorated credit quality	2,108,000
Residential real estate [Member]
Allowance for Loan Losses:
Beginning balance	11,653,000
Charge-offs	7,069,000
Recoveries	248,000
Provision	9,048,000
Ending balance	13,880,000
Ending Balance: individually evaluated for impairment	1,925,000
Ending Balance: collectively evaluated for impairment	11,955,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	1,897,658,000
Ending balance: individually evaluated for impairment	18,288,000
Ending balance: collectively evaluated for impairment	1,877,287,000
Ending Balance: loans acquired with deteriorated credit quality	2,083,000
Construction and Land Development [Member]
Allowance for Loan Losses:
Beginning balance	18,738,000
Charge-offs	6,290,000
Recoveries	136,000
Provision	6,567,000
Ending balance	19,151,000
Ending Balance: individually evaluated for impairment	2,480,000
Ending Balance: collectively evaluated for impairment	16,671,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	549,877,000
Ending balance: individually evaluated for impairment	20,835,000
Ending balance: collectively evaluated for impairment	508,921,000
Ending Balance: loans acquired with deteriorated credit quality	20,121,000
Consumer [Member]
Allowance for Loan Losses:
Beginning balance	2,161,000
Charge-offs	1,354,000
Recoveries	356,000
Provision	988,000
Ending balance	2,151,000
Ending Balance: individually evaluated for impairment	0
Ending Balance: collectively evaluated for impairment	2,151,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	283,712,000
Ending balance: individually evaluated for impairment	0
Ending balance: collectively evaluated for impairment	280,947,000
Ending Balance: loans acquired with deteriorated credit quality	2,765,000
Allowance for Estimated Imprecision [Member]
Allowance for Loan Losses:
Beginning balance	2,991,000
Charge-offs	0
Recoveries	0
Provision	(419,000)
Ending balance	2,572,000
Ending Balance: individually evaluated for impairment	0
Ending Balance: collectively evaluated for impairment	2,572,000
Ending Balance: loans acquired with deteriorated credit quality	0
Financing receivables:
Financing receivable, Ending balance	0
Ending balance: individually evaluated for impairment	0
Ending balance: collectively evaluated for impairment	0
Ending Balance: loans acquired with deteriorated credit quality	$ 0