Loans, Allowance for Loan and Lease Losses, and Reserve for Off-Balance Sheet Credit Commitments (Detail 5) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Recorded Investment
With no related allowance recorded	$ 35,176	$ 58,090	$ 35,176	$ 58,090	$ 45,611
With an allowance recorded	15,269	31,525	15,269	31,525	15,611
Total impaired loans	50,445	89,615	50,445	89,615	61,222
Unpaid Contractual Principal Balance
With no related allowance recorded	44,644	76,501	44,644	76,501	51,987
With an allowance recorded	15,678	38,083	15,678	38,083	18,352
Total impaired loans	60,322	114,584	60,322	114,584	70,339
Related Allowance
Total impaired loans	1,595	8,833	1,595	8,833	728
Average Recorded Investment
With no related allowance recorded	36,049	68,025	39,236	71,840
With an allowance recorded	15,199	27,158	15,336	25,170
Total impaired loans	51,248	95,183	54,572	97,010
Interest Income Recognized
With no related allowance recorded	283	356	568	1,044
With an allowance recorded	123	86	237	130
Total impaired loans	406	442	805	1,174
Commercial
Recorded Investment
With no related allowance recorded	2,453	6,980	2,453	6,980	8,894
With an allowance recorded	6,338	22,251	6,338	22,251	6,470
Total impaired loans	8,791	29,231	8,791	29,231	15,364
Unpaid Contractual Principal Balance
With no related allowance recorded	8,364	7,713	8,364	7,713	9,182
With an allowance recorded	6,431	28,454	6,431	28,454	8,878
Total impaired loans	14,795	36,167	14,795	36,167	18,060
Related Allowance
Total impaired loans	1,299	8,477	1,299	8,477	399
Average Recorded Investment
With no related allowance recorded	1,951	9,118	4,265	11,986
With an allowance recorded	6,245	19,839	6,320	17,938
Total impaired loans	8,196	28,957	10,585	29,924
Interest Income Recognized
With no related allowance recorded	18	30	23	167
With an allowance recorded	26		43
Total impaired loans	44	30	66	167
Commercial real estate mortgages
Recorded Investment
With no related allowance recorded	17,974	28,233	17,974	28,233	19,858
With an allowance recorded	5,019	5,223	5,019	5,223	5,184
Total impaired loans	22,993	33,456	22,993	33,456	25,042
Unpaid Contractual Principal Balance
With no related allowance recorded	19,067	30,829	19,067	30,829	22,416
With an allowance recorded	5,343	5,586	5,343	5,586	5,526
Total impaired loans	24,410	36,415	24,410	36,415	27,942
Related Allowance
Total impaired loans	263	301	263	301	281
Average Recorded Investment
With no related allowance recorded	17,906	32,398	18,557	32,522
With an allowance recorded	5,030	5,293	5,081	5,323
Total impaired loans	22,936	37,691	23,638	37,845
Interest Income Recognized
With no related allowance recorded	197	246	405	684
With an allowance recorded	71	74	142	118
Total impaired loans	268	320	547	802
Residential mortgages
Recorded Investment
With no related allowance recorded	8,000	6,595	8,000	6,595	7,980
With an allowance recorded	3,912	4,001	3,912	4,001	3,957
Total impaired loans	11,912	10,596	11,912	10,596	11,937
Unpaid Contractual Principal Balance
With no related allowance recorded	8,271	6,934	8,271	6,934	8,256
With an allowance recorded	3,904	3,993	3,904	3,993	3,948
Total impaired loans	12,175	10,927	12,175	10,927	12,204
Related Allowance
Total impaired loans	33	5	33	5	48
Average Recorded Investment
With no related allowance recorded	7,860	7,250	7,900	7,346
With an allowance recorded	3,924	2,001	3,935	1,892
Total impaired loans	11,784	9,251	11,835	9,238
Interest Income Recognized
With no related allowance recorded	16	24	26	48
With an allowance recorded	26	11	52	11
Total impaired loans	42	35	78	59
Fixed
Recorded Investment
With no related allowance recorded	8,000	4,796	8,000	4,796	7,756
Unpaid Contractual Principal Balance
With no related allowance recorded	8,271	5,012	8,271	5,012	7,994
Average Recorded Investment
With no related allowance recorded	7,860	4,842	7,825	3,940
Interest Income Recognized
With no related allowance recorded	16	10	26	20
Variable
Recorded Investment
With no related allowance recorded		1,799		1,799	224
With an allowance recorded	3,912	4,001	3,912	4,001	3,957
Unpaid Contractual Principal Balance
With no related allowance recorded		1,922		1,922	262
With an allowance recorded	3,904	3,993	3,904	3,993	3,948
Related Allowance
Total impaired loans	33		33		48
Average Recorded Investment
With no related allowance recorded		2,408	75	3,406
With an allowance recorded	3,924	2,001	3,935	1,892
Interest Income Recognized
With no related allowance recorded		14		28
With an allowance recorded	26	11	52	11
Real estate construction
Recorded Investment
With no related allowance recorded	5,816	12,846	5,816	12,846	6,609
Total impaired loans	5,816	12,846	5,816	12,846	6,609
Unpaid Contractual Principal Balance
With no related allowance recorded	6,900	26,520	6,900	26,520	8,758
Total impaired loans	6,900	26,520	6,900	26,520	8,758
Average Recorded Investment
With no related allowance recorded	7,398	15,817	7,135	16,910
Total impaired loans	7,398	15,817	7,135	16,910
Interest Income Recognized
With no related allowance recorded	52	56	114	145
Total impaired loans	52	56	114	145
Construction
Average Recorded Investment
With no related allowance recorded		2,742		3,656
Interest Income Recognized
With no related allowance recorded		21		76
Land.
Recorded Investment
With no related allowance recorded	5,816	12,846	5,816	12,846	6,609
Unpaid Contractual Principal Balance
With no related allowance recorded	6,900	26,520	6,900	26,520	8,758
Average Recorded Investment
With no related allowance recorded	7,398	13,075	7,135	13,254
Interest Income Recognized
With no related allowance recorded	52	35	114	69
Home equity loans and lines of credit
Recorded Investment
With no related allowance recorded	933	3,436	933	3,436	2,270
Total impaired loans	933	3,436	933	3,436	2,270
Unpaid Contractual Principal Balance
With no related allowance recorded	2,042	4,505	2,042	4,505	3,375
Total impaired loans	2,042	4,505	2,042	4,505	$ 3,375
Average Recorded Investment
With no related allowance recorded	934	3,442	1,379	3,071
Total impaired loans	$ 934	3,442	$ 1,379	3,071
Installment
Recorded Investment
With no related allowance recorded		50		50
With an allowance recorded		50		50
Unpaid Contractual Principal Balance
With no related allowance recorded		50		50
With an allowance recorded		50		50
Related Allowance
Total impaired loans		50		50
Average Recorded Investment
With no related allowance recorded				5
With an allowance recorded		25		17
Total impaired loans		25		22
Interest Income Recognized
With no related allowance recorded				1
With an allowance recorded		1		1
Total impaired loans		1
Consumer Installment loan
Recorded Investment
With an allowance recorded		50		50
Unpaid Contractual Principal Balance
With an allowance recorded		50		50
Related Allowance
Total impaired loans		50		50
Average Recorded Investment
With no related allowance recorded				5
With an allowance recorded		25		17
Interest Income Recognized
With an allowance recorded		$ 1		$ 1