Loans and Allowance for Loan Losses - Summary of Impaired Loans Disaggregated by Class (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	$ 21,141	$ 41,526
Recorded Investment, With a related allowance recorded	30,766	42,052
Recorded Investment, Total	51,907	83,578
Unpaid Principal Balance, With no related allowance recorded	24,869	70,970
Unpaid Principal Balance, With a related allowance recorded	31,408	44,303
Unpaid Principal Balance, Total	56,277	115,273
Related Allowance, Total	1,945	7,165
Average Recorded Investment, With no related allowance recorded	24,973	33,502
Average Recorded Investment, With a related allowance recorded	43,349	47,402
Average Recorded Investment, Total	68,322	80,904
Interest Income Recognized, With no related allowance recorded	456	619
Interest Income Recognized, With a related allowance recorded	683	703
Interest Income Recognized, Total	1,139	1,322
Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	3,027
Recorded Investment, With a related allowance recorded	8,063
Recorded Investment, Total	11,090
Unpaid Principal Balance, With no related allowance recorded	3,259
Unpaid Principal Balance, With a related allowance recorded	8,365
Unpaid Principal Balance, Total	11,624
Related Allowance, Total	325
Average Recorded Investment, With no related allowance recorded	757
Average Recorded Investment, With a related allowance recorded	13,363
Average Recorded Investment, Total	14,120
Interest Income Recognized, With no related allowance recorded	12
Interest Income Recognized, With a related allowance recorded	230
Interest Income Recognized, Total	242
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	10,528
Recorded Investment, With a related allowance recorded	6,246
Recorded Investment, Total	16,774
Unpaid Principal Balance, With no related allowance recorded	12,185
Unpaid Principal Balance, With a related allowance recorded	6,246
Unpaid Principal Balance, Total	18,431
Related Allowance, Total	211
Average Recorded Investment, With no related allowance recorded	2,633
Average Recorded Investment, With a related allowance recorded	1,759
Average Recorded Investment, Total	4,392
Interest Income Recognized, With no related allowance recorded	53
Interest Income Recognized, With a related allowance recorded	40
Interest Income Recognized, Total	93
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	7,084
Recorded Investment, With a related allowance recorded	16,457
Recorded Investment, Total	23,541
Unpaid Principal Balance, With no related allowance recorded	8,916
Unpaid Principal Balance, With a related allowance recorded	16,797
Unpaid Principal Balance, Total	25,713
Related Allowance, Total	1,409
Average Recorded Investment, With no related allowance recorded	19,606
Average Recorded Investment, With a related allowance recorded	25,755
Average Recorded Investment, Total	45,361
Interest Income Recognized, With no related allowance recorded	391
Interest Income Recognized, With a related allowance recorded	413
Interest Income Recognized, Total	804
Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	502	3,114
Recorded Investment, With a related allowance recorded
Recorded Investment, Total	502	3,114
Unpaid Principal Balance, With no related allowance recorded	509	5,661
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total	509	5,661
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	710	3,701
Average Recorded Investment, With a related allowance recorded	1,191	4,619
Average Recorded Investment, Total	1,901	8,320
Interest Income Recognized, With no related allowance recorded		155
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total		155
Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	1,267
Average Recorded Investment, With a related allowance recorded	1,281
Average Recorded Investment, Total	2,548
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded		38,412
Recorded Investment, With a related allowance recorded		42,052
Recorded Investment, Total		80,464
Unpaid Principal Balance, With no related allowance recorded		65,309
Unpaid Principal Balance, With a related allowance recorded		44,303
Unpaid Principal Balance, Total		109,612
Related Allowance, Total		7,165
Average Recorded Investment, With no related allowance recorded		29,801
Average Recorded Investment, With a related allowance recorded		42,783
Average Recorded Investment, Total		72,584
Interest Income Recognized, With no related allowance recorded		464
Interest Income Recognized, With a related allowance recorded		703
Interest Income Recognized, Total		1,167
Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	17,254	37,426
Recorded Investment, With a related allowance recorded	28,871	35,850
Recorded Investment, Total	46,125	73,276
Unpaid Principal Balance, With no related allowance recorded	20,934	59,975
Unpaid Principal Balance, With a related allowance recorded	29,477	37,917
Unpaid Principal Balance, Total	50,411	97,892
Related Allowance, Total	1,482	6,377
Average Recorded Investment, With no related allowance recorded	22,784	27,048
Average Recorded Investment, With a related allowance recorded	35,333	45,851
Average Recorded Investment, Total	58,117	72,899
Interest Income Recognized, With no related allowance recorded	409	619
Interest Income Recognized, With a related allowance recorded	620	703
Interest Income Recognized, Total	1,029	1,322
Originated loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	848
Recorded Investment, With a related allowance recorded	8,063
Recorded Investment, Total	8,911
Unpaid Principal Balance, With no related allowance recorded	1,073
Unpaid Principal Balance, With a related allowance recorded	8,365
Unpaid Principal Balance, Total	9,438
Related Allowance, Total	325
Average Recorded Investment, With no related allowance recorded	212
Average Recorded Investment, With a related allowance recorded	9,929
Average Recorded Investment, Total	10,141
Interest Income Recognized, With no related allowance recorded	12
Interest Income Recognized, With a related allowance recorded	167
Interest Income Recognized, Total	179
Originated loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	9,798
Recorded Investment, With a related allowance recorded	6,246
Recorded Investment, Total	16,044
Unpaid Principal Balance, With no related allowance recorded	11,431
Unpaid Principal Balance, With a related allowance recorded	6,246
Unpaid Principal Balance, Total	17,677
Related Allowance, Total	211
Average Recorded Investment, With no related allowance recorded	2,450
Average Recorded Investment, With a related allowance recorded	1,562
Average Recorded Investment, Total	4,012
Interest Income Recognized, With no related allowance recorded	53
Interest Income Recognized, With a related allowance recorded	40
Interest Income Recognized, Total	93
Originated loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	6,608
Recorded Investment, With a related allowance recorded	14,562
Recorded Investment, Total	21,170
Unpaid Principal Balance, With no related allowance recorded	8,430
Unpaid Principal Balance, With a related allowance recorded	14,866
Unpaid Principal Balance, Total	23,296
Related Allowance, Total	946
Average Recorded Investment, With no related allowance recorded	18,527
Average Recorded Investment, With a related allowance recorded	22,427
Average Recorded Investment, Total	40,954
Interest Income Recognized, With no related allowance recorded	344
Interest Income Recognized, With a related allowance recorded	413
Interest Income Recognized, Total	757
Originated loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded		2,721
Recorded Investment, With a related allowance recorded
Recorded Investment, Total		2,721
Unpaid Principal Balance, With no related allowance recorded		4,874
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total		4,874
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	328	3,255
Average Recorded Investment, With a related allowance recorded	134	4,619
Average Recorded Investment, Total	462	7,874
Interest Income Recognized, With no related allowance recorded		155
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total		155
Originated loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	1,267
Average Recorded Investment, With a related allowance recorded	1,281
Average Recorded Investment, Total	2,548
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Originated loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded		34,705
Recorded Investment, With a related allowance recorded		35,850
Recorded Investment, Total		70,555
Unpaid Principal Balance, With no related allowance recorded		55,101
Unpaid Principal Balance, With a related allowance recorded		37,917
Unpaid Principal Balance, Total		93,018
Related Allowance, Total		6,377
Average Recorded Investment, With no related allowance recorded		23,793
Average Recorded Investment, With a related allowance recorded		41,232
Average Recorded Investment, Total		65,025
Interest Income Recognized, With no related allowance recorded		464
Interest Income Recognized, With a related allowance recorded		703
Interest Income Recognized, Total		1,167
Acquired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	3,887
Recorded Investment, With a related allowance recorded	1,895	6,202
Recorded Investment, Total	5,782	6,202
Unpaid Principal Balance, With no related allowance recorded	3,935
Unpaid Principal Balance, With a related allowance recorded	1,931	6,386
Unpaid Principal Balance, Total	5,866	6,386
Related Allowance, Total	463	788
Average Recorded Investment, With no related allowance recorded	2,189
Average Recorded Investment, With a related allowance recorded	8,016	1,551
Average Recorded Investment, Total	10,205	1,551
Interest Income Recognized, With no related allowance recorded	47
Interest Income Recognized, With a related allowance recorded	63
Interest Income Recognized, Total	110
Acquired loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	2,179
Recorded Investment, With a related allowance recorded
Recorded Investment, Total	2,179
Unpaid Principal Balance, With no related allowance recorded	2,186
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total	2,186
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	545
Average Recorded Investment, With a related allowance recorded	3,434
Average Recorded Investment, Total	3,979
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded	63
Interest Income Recognized, Total	63
Acquired loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	730
Recorded Investment, With a related allowance recorded
Recorded Investment, Total	730
Unpaid Principal Balance, With no related allowance recorded	754
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total	754
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	183
Average Recorded Investment, With a related allowance recorded	197
Average Recorded Investment, Total	380
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Acquired loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	476
Recorded Investment, With a related allowance recorded	1,895
Recorded Investment, Total	2,371
Unpaid Principal Balance, With no related allowance recorded	486
Unpaid Principal Balance, With a related allowance recorded	1,931
Unpaid Principal Balance, Total	2,417
Related Allowance, Total	463
Average Recorded Investment, With no related allowance recorded	1,079
Average Recorded Investment, With a related allowance recorded	3,328
Average Recorded Investment, Total	4,407
Interest Income Recognized, With no related allowance recorded	47
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total	47
Acquired loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	502
Recorded Investment, With a related allowance recorded
Recorded Investment, Total	502
Unpaid Principal Balance, With no related allowance recorded	509
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total	509
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded	382
Average Recorded Investment, With a related allowance recorded	1,057
Average Recorded Investment, Total	1,439
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Acquired loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Acquired loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded		6,202
Recorded Investment, Total		6,202
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded		6,386
Unpaid Principal Balance, Total		6,386
Related Allowance, Total		788
Average Recorded Investment, With a related allowance recorded		1,551
Average Recorded Investment, Total		1,551
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded		4,100
Recorded Investment, With a related allowance recorded
Recorded Investment, Total		4,100
Unpaid Principal Balance, With no related allowance recorded		10,995
Unpaid Principal Balance, Total		10,995
Average Recorded Investment, With no related allowance recorded		6,454
Average Recorded Investment, Total		6,454
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded
Average Recorded Investment, Total
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded		393
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded		787
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded		446
Average Recorded Investment, Total
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member] | Residential Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total		393
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total		787
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded
Average Recorded Investment, Total		446
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member] | Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded
Recorded Investment, With a related allowance recorded
Recorded Investment, Total
Unpaid Principal Balance, With no related allowance recorded
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total
Related Allowance, Total
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total
Covered loans [Member] | Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded		3,707
Recorded Investment, With a related allowance recorded
Recorded Investment, Total		3,707
Unpaid Principal Balance, With no related allowance recorded		10,208
Unpaid Principal Balance, With a related allowance recorded
Unpaid Principal Balance, Total		10,208
Related Allowance, Total
Average Recorded Investment, With no related allowance recorded		6,008
Average Recorded Investment, Total		6,008
Interest Income Recognized, With no related allowance recorded
Interest Income Recognized, With a related allowance recorded
Interest Income Recognized, Total