Income Tax (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Contingency [Line Items]
State operating loss carryforwards, set to begin to expire in 2023	$ 25,300,000								$ 25,300,000
State tax credit carryforwards, set to expire in 2014	1,700,000								1,700,000
Current tax (benefit) expense									21,581,000	21,218,000	21,688,000
Deferred tax expense (benefit)									5,413,000	(3,656,000)	(3,783,000)
Income tax expense (benefit)	7,911,000	6,734,000	7,414,000	4,935,000	5,342,000	4,655,000	4,367,000	3,198,000	26,994,000	17,562,000	17,905,000
Deferred tax assets:
Allowance for loan and lease losses	27,196,000				30,027,000				27,196,000	30,027,000
Supplemental executive retirement plan	8,565,000				6,967,000				8,565,000	6,967,000
Stock option and restricted stock	917,000				682,000				917,000	682,000
OREO costs	7,929,000				3,801,000				7,929,000	3,801,000
Nonaccrual interest	2,354,000				193,000				2,354,000	193,000
Deferred tax assets, purchase accounting	15,551,000				0				15,551,000	0
Deferred Tax Assets, Unrealized Losses on Available-for-Sale Securities, Gross	7,176,000				0				7,176,000	0
deferred tax liabilities, unrealized gains on available-for-sale securities	0				11,150,000				0	11,150,000
Other	1,741,000				557,000				1,741,000	557,000
Total deferred tax assets	71,429,000				42,227,000				71,429,000	42,227,000
Deferred tax liabilities:
Asset purchase tax basis difference	(7,754,000)				(19,408,000)				(7,754,000)	(19,408,000)
FHLB stock dividends	(4,159,000)				(1,963,000)				(4,159,000)	(1,963,000)
Purchase accounting	0				(745,000)				0	(745,000)
Deferred loan fees	(4,512,000)				(1,755,000)				(4,512,000)	(1,755,000)
Depreciation	(7,076,000)				(1,870,000)				(7,076,000)	(1,870,000)
Total deferred tax liabilities	23,501,000				36,891,000				23,501,000	36,891,000
Net deferred tax (liability) asset	47,928,000				5,336,000				47,928,000	5,336,000
Reconciliation of effective income tax rate with federal statutory tax rate
Income tax based on statutory rate									30,454,000	22,297,000	23,080,000
Income tax based on statutory rate, percent									35.00%	35.00%	35.00%
Tax credits									(1,038,000)	(504,000)	(608,000)
Tax credits, percent									(1.00%)	(1.00%)	(1.00%)
Tax exempt instrument									(4,113,000)	(3,906,000)	(3,824,000)
Tax exempt instrument, percent									(5.00%)	(6.00%)	(6.00%)
Life insurance proceeds									(1,250,000)	(1,001,000)	(766,000)
Life insurance proceeds, percent									(1.00%)	(2.00%)	(1.00%)
Bargain purchase									0	0	(1,036,000)
Bargain purchase, percent									0.00%	0.00%	(2.00%)
effective income tax rate reconciliation, nondeductible expense, business combination, amount									1,362,000	0	0
effective income tax rate reconciliation, nondeductible expense, business combination, percent									2.00%	0.00%	0.00%
Other, net									1,579,000	676,000	1,059,000
Other, net, percent									1.00%	1.00%	2.00%
Income tax expense (benefit)	7,911,000	6,734,000	7,414,000	4,935,000	5,342,000	4,655,000	4,367,000	3,198,000	26,994,000	17,562,000	17,905,000
Income tax provision (benefit), percent									31.00%	27.00%	27.00%
Unrecognized tax position	0								0
Interest and penalties on unrecognized tax benefits									$ 0