Loans and Leases - Summary of Impaired Loans, by Class (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	$ 79,186	$ 81,765
Recorded Investment With No Specific Reserve	64,979	66,619
Recorded Investment With Specific Reserve	2,940	2,831
Total Recorded Investment	67,919	69,450
Specific Reserve	2,181	1,179
Average Recorded Investment	69,663	75,367
Commercial Real Estate [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	34,483	34,583
Recorded Investment With No Specific Reserve	25,015	25,443
Recorded Investment With Specific Reserve	1,012	883
Total Recorded Investment	26,027	26,326
Specific Reserve	735	399
Average Recorded Investment	26,176	30,807
Commercial and Industrial [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	11,251	11,412
Recorded Investment With No Specific Reserve	8,138	7,609
Recorded Investment With Specific Reserve	1,928	1,948
Total Recorded Investment	10,066	9,557
Specific Reserve	1,446	780
Average Recorded Investment	9,811	9,510
Commercial Leases [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	732	722
Recorded Investment With No Specific Reserve	732	722
Total Recorded Investment	732	722
Average Recorded Investment	727	686
Total Commercial Loans and Leases [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	46,466	46,717
Recorded Investment With No Specific Reserve	33,885	33,774
Recorded Investment With Specific Reserve	2,940	2,831
Total Recorded Investment	36,825	36,605
Specific Reserve	2,181	1,179
Average Recorded Investment	36,714	41,003
Direct Installment [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	13,977	14,987
Recorded Investment With No Specific Reserve	13,768	14,680
Total Recorded Investment	13,768	14,680
Average Recorded Investment	14,343	14,248
Residential Mortgages [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	15,718	16,791
Recorded Investment With No Specific Reserve	14,472	15,064
Total Recorded Investment	14,472	15,064
Average Recorded Investment	15,547	16,924
Indirect Installment [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	1,425	1,467
Recorded Investment With No Specific Reserve	1,265	1,305
Total Recorded Investment	1,265	1,305
Average Recorded Investment	1,363	1,399
Consumer Lines of Credit [Member]
Financial Receivables Impaired Or Restructured [Line Items]
Unpaid Contractual Principal Balance	1,600	1,803
Recorded Investment With No Specific Reserve	1,589	1,796
Total Recorded Investment	1,589	1,796
Average Recorded Investment	$ 1,696	$ 1,793

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5258-111524

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953550-111524

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