Loans - Summary of Impaired Loans Disaggregated by Class (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	$ 55,034	$ 14,815
Recorded Investment, With a related allowance recorded	58,392	14,896
Recorded Investment, Total	113,426	29,711
Unpaid Principal Balance, With no related allowance recorded	58,245	20,707
Unpaid Principal Balance, With a related allowance recorded	60,378	15,581
Unpaid Principal Balance, Total	118,623	36,288
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	20,988	854
Related Allowance, Total	20,988	854
Average Recorded Investment, With no related allowance recorded	32,585	13,965
Average Recorded Investment, With a related allowance recorded	41,599	25,340
Average Recorded Investment, Total	74,184	39,305
Interest Income Recognized, With no related allowance recorded	37	527
Interest Income Recognized, With a related allowance recorded	205	648
Interest Income Recognized, Total	242	1,175
Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	34,788	3,003
Recorded Investment, With a related allowance recorded	46,834	984
Recorded Investment, Total	81,622	3,987
Unpaid Principal Balance, With no related allowance recorded	37,285	3,646
Unpaid Principal Balance, With a related allowance recorded	47,703	984
Unpaid Principal Balance, Total	84,988	4,630
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	19,031	14
Related Allowance, Total	19,031	14
Average Recorded Investment, With no related allowance recorded	18,860	1,566
Average Recorded Investment, With a related allowance recorded	22,414	6,581
Average Recorded Investment, Total	41,274	8,147
Interest Income Recognized, With no related allowance recorded		51
Interest Income Recognized, With a related allowance recorded	11	221
Interest Income Recognized, Total	11	272
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	12,461	3,345
Recorded Investment, With a related allowance recorded	1,765	4,905
Recorded Investment, Total	14,226	8,250
Unpaid Principal Balance, With no related allowance recorded	12,461	6,486
Unpaid Principal Balance, With a related allowance recorded	2,323	4,906
Unpaid Principal Balance, Total	14,784	11,392
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	392	19
Related Allowance, Total	392	19
Average Recorded Investment, With no related allowance recorded	2,459	3,451
Average Recorded Investment, With a related allowance recorded	3,049	7,697
Average Recorded Investment, Total	5,508	11,148
Interest Income Recognized, With no related allowance recorded		142
Interest Income Recognized, With a related allowance recorded	66	193
Interest Income Recognized, Total	66	335
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	7,785	8,467
Recorded Investment, With a related allowance recorded	8,746	6,345
Recorded Investment, Total	16,531	14,812
Unpaid Principal Balance, With no related allowance recorded	8,499	10,575
Unpaid Principal Balance, With a related allowance recorded	8,795	6,374
Unpaid Principal Balance, Total	17,294	16,949
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	1,405	488
Related Allowance, Total	1,405	488
Average Recorded Investment, With no related allowance recorded	10,933	8,772
Average Recorded Investment, With a related allowance recorded	14,732	8,857
Average Recorded Investment, Total	25,665	17,629
Interest Income Recognized, With no related allowance recorded	35	331
Interest Income Recognized, With a related allowance recorded	104	184
Interest Income Recognized, Total	139	515
Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With a related allowance recorded	895	2,656
Recorded Investment, Total	895	2,656
Unpaid Principal Balance, With a related allowance recorded	1,405	3,311
Unpaid Principal Balance, Total	1,405	3,311
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	127	330
Related Allowance, Total	127	330
Average Recorded Investment, With no related allowance recorded	259	176
Average Recorded Investment, With a related allowance recorded	1,359	2,204
Average Recorded Investment, Total	1,618	2,380
Interest Income Recognized, With no related allowance recorded	2	3
Interest Income Recognized, With a related allowance recorded	20	50
Interest Income Recognized, Total	22	53
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With a related allowance recorded	152	6
Recorded Investment, Total	152	6
Unpaid Principal Balance, With a related allowance recorded	152	6
Unpaid Principal Balance, Total	152	6
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	33	3
Related Allowance, Total	33	3
Average Recorded Investment, With no related allowance recorded	74
Average Recorded Investment, With a related allowance recorded	45	1
Average Recorded Investment, Total	119	1
Interest Income Recognized, With a related allowance recorded	4
Interest Income Recognized, Total	4
Originated Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	55,034	14,815
Recorded Investment, With a related allowance recorded	56,052	12,205
Recorded Investment, Total	111,086	27,020
Unpaid Principal Balance, With no related allowance recorded	58,245	20,707
Unpaid Principal Balance, With a related allowance recorded	57,996	12,861
Unpaid Principal Balance, Total	116,241	33,568
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	20,955	377
Related Allowance, Total	20,955	377
Average Recorded Investment, With no related allowance recorded	32,585	13,088
Average Recorded Investment, With a related allowance recorded	39,355	21,887
Average Recorded Investment, Total	71,940	34,976
Interest Income Recognized, With no related allowance recorded	37	527
Interest Income Recognized, With a related allowance recorded	205	395
Interest Income Recognized, Total	242	921
Originated Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	34,788	3,003
Recorded Investment, With a related allowance recorded	46,834	984
Recorded Investment, Total	81,622	3,987
Unpaid Principal Balance, With no related allowance recorded	37,285	3,646
Unpaid Principal Balance, With a related allowance recorded	47,703	984
Unpaid Principal Balance, Total	84,988	4,630
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	19,031	14
Related Allowance, Total	19,031	14
Average Recorded Investment, With no related allowance recorded	18,860	1,209
Average Recorded Investment, With a related allowance recorded	22,414	5,522
Average Recorded Investment, Total	41,274	6,732
Interest Income Recognized, With no related allowance recorded		51
Interest Income Recognized, With a related allowance recorded	11	99
Interest Income Recognized, Total	11	150
Originated Loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	12,461	3,345
Recorded Investment, With a related allowance recorded	1,765	4,905
Recorded Investment, Total	14,226	8,250
Unpaid Principal Balance, With no related allowance recorded	12,461	6,486
Unpaid Principal Balance, With a related allowance recorded	2,323	4,906
Unpaid Principal Balance, Total	14,784	11,392
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	392	19
Related Allowance, Total	392	19
Average Recorded Investment, With no related allowance recorded	2,459	3,330
Average Recorded Investment, With a related allowance recorded	3,049	6,660
Average Recorded Investment, Total	5,508	9,990
Interest Income Recognized, With no related allowance recorded		142
Interest Income Recognized, With a related allowance recorded	66	137
Interest Income Recognized, Total	66	279
Originated Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With no related allowance recorded	7,785	8,467
Recorded Investment, With a related allowance recorded	6,406	3,654
Recorded Investment, Total	14,191	12,121
Unpaid Principal Balance, With no related allowance recorded	8,499	10,575
Unpaid Principal Balance, With a related allowance recorded	6,413	3,654
Unpaid Principal Balance, Total	14,912	14,229
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	1,372	11
Related Allowance, Total	1,372	11
Average Recorded Investment, With no related allowance recorded	10,933	8,461
Average Recorded Investment, With a related allowance recorded	12,488	7,500
Average Recorded Investment, Total	23,421	15,961
Interest Income Recognized, With no related allowance recorded	35	331
Interest Income Recognized, With a related allowance recorded	104	109
Interest Income Recognized, Total	139	439
Originated Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With a related allowance recorded	895	2,656
Recorded Investment, Total	895	2,656
Unpaid Principal Balance, With a related allowance recorded	1,405	3,311
Unpaid Principal Balance, Total	1,405	3,311
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	127	330
Related Allowance, Total	127	330
Average Recorded Investment, With no related allowance recorded	259	88
Average Recorded Investment, With a related allowance recorded	1,359	2,204
Average Recorded Investment, Total	1,618	2,292
Interest Income Recognized, With no related allowance recorded	2	3
Interest Income Recognized, With a related allowance recorded	20	50
Interest Income Recognized, Total	22	53
Originated Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With a related allowance recorded	152	6
Recorded Investment, Total	152	6
Unpaid Principal Balance, With a related allowance recorded	152	6
Unpaid Principal Balance, Total	152	6
Related Allowance, With no related allowance recorded	0	0
Related Allowance, With a related allowance recorded	33	3
Related Allowance, Total	33	3
Average Recorded Investment, With no related allowance recorded	74
Average Recorded Investment, With a related allowance recorded	45	1
Average Recorded Investment, Total	119	1
Interest Income Recognized, With a related allowance recorded	4
Interest Income Recognized, Total	4
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With a related allowance recorded	2,340	2,691
Recorded Investment, Total	2,340	2,691
Unpaid Principal Balance, With a related allowance recorded	2,382	2,720
Unpaid Principal Balance, Total	2,382	2,720
Related Allowance, With no related allowance recorded		0
Related Allowance, With a related allowance recorded	33	477
Related Allowance, Total	33	477
Average Recorded Investment, With no related allowance recorded		877
Average Recorded Investment, With a related allowance recorded	2,244	3,453
Average Recorded Investment, Total	2,244	4,330
Interest Income Recognized, With a related allowance recorded		253
Interest Income Recognized, Total		253
Acquired Loans [Member] | Commercial Non-Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Related Allowance, With no related allowance recorded		0
Average Recorded Investment, With no related allowance recorded		357
Average Recorded Investment, With a related allowance recorded		1,059
Average Recorded Investment, Total		1,416
Interest Income Recognized, With a related allowance recorded		122
Interest Income Recognized, Total		122
Acquired Loans [Member] | Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Related Allowance, With no related allowance recorded		0
Average Recorded Investment, With no related allowance recorded		121
Average Recorded Investment, With a related allowance recorded		1,037
Average Recorded Investment, Total		1,158
Interest Income Recognized, With a related allowance recorded		56
Interest Income Recognized, Total		56
Acquired Loans [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded Investment, With a related allowance recorded	2,340	2,691
Recorded Investment, Total	2,340	2,691
Unpaid Principal Balance, With a related allowance recorded	2,382	2,720
Unpaid Principal Balance, Total	2,382	2,720
Related Allowance, With no related allowance recorded		0
Related Allowance, With a related allowance recorded	33	477
Related Allowance, Total	33	477
Average Recorded Investment, With no related allowance recorded		311
Average Recorded Investment, With a related allowance recorded	2,244	1,357
Average Recorded Investment, Total	$ 2,244	1,668
Interest Income Recognized, With a related allowance recorded		75
Interest Income Recognized, Total		75
Acquired Loans [Member] | Residential Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Related Allowance, With no related allowance recorded		0
Average Recorded Investment, With no related allowance recorded		88
Average Recorded Investment, Total		88
Acquired Loans [Member] | Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Related Allowance, With no related allowance recorded		$ 0