Allowance for Credit Losses and Credit Quality - Schedule of Investment in Impaired Loan (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 33,545		$ 45,342
Unpaid Principal Balance	34,306		46,501
Related Allowance	(761)		(1,159)
Average Recorded Investment	34,535	52,440
Interest Income Recognized	28	59
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,497		25,018
Unpaid Principal Balance	13,969		25,877
Related Allowance	(472)		(859)
Average Recorded Investment	14,154	34,148
Interest Income Recognized	28	59
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,515		8,567
Unpaid Principal Balance	7,515		8,567
Related Allowance
Average Recorded Investment	7,493	30,510
Interest Income Recognized		28
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Business [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,088		13,256
Unpaid Principal Balance	2,088		13,256
Related Allowance
Average Recorded Investment	2,107	3,030
Interest Income Recognized		24
Commercial Loans [Member] | With No Related Allowance Recorded [Member] | Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	253		258
Unpaid Principal Balance	253		258
Related Allowance
Average Recorded Investment	255
Interest Income Recognized
Commercial Loans [Member] | With An Allowance Recorded [Member] | Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,166		1,268
Unpaid Principal Balance	1,172		1,284
Related Allowance	(6)		(16)
Average Recorded Investment	1,223	157
Interest Income Recognized	8	2
Commercial Loans [Member] | With An Allowance Recorded [Member] | Business [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,728		1,927
Unpaid Principal Balance	3,194		2,770
Related Allowance	(466)		(843)
Average Recorded Investment	3,331	451
Interest Income Recognized	20	5
Mortgage Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	10,524		11,408
Unpaid Principal Balance	10,755		11,645
Related Allowance	(231)		(237)
Average Recorded Investment	10,460	9,213
Interest Income Recognized
Mortgage Loans [Member] | With An Allowance Recorded [Member] | Residential Prime [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	8,905		9,791
Unpaid Principal Balance	9,129		10,019
Related Allowance	(224)		(228)
Average Recorded Investment	8,834	9,213
Interest Income Recognized
Mortgage Loans [Member] | With An Allowance Recorded [Member] | Residential Subprime [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,619		1,617
Unpaid Principal Balance	1,626		1,626
Related Allowance	(7)		(9)
Average Recorded Investment	1,626
Interest Income Recognized
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	9,524		8,916
Unpaid Principal Balance	9,582		8,979
Related Allowance	(58)		(63)
Average Recorded Investment	9,921	9,079
Interest Income Recognized
Consumer Loans [Member] | With An Allowance Recorded [Member] | Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,165		6,506
Unpaid Principal Balance	7,205		6,550
Related Allowance	(40)		(44)
Average Recorded Investment	7,331	6,910
Interest Income Recognized
Consumer Loans [Member] | With An Allowance Recorded [Member] | Indirect Automobile [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,322		1,267
Unpaid Principal Balance	1,330		1,275
Related Allowance	(8)		(8)
Average Recorded Investment	1,474	1,267
Interest Income Recognized
Consumer Loans [Member] | With An Allowance Recorded [Member] | Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	320		404
Unpaid Principal Balance	326		411
Related Allowance	(6)		(7)
Average Recorded Investment	370	405
Interest Income Recognized
Consumer Loans [Member] | With An Allowance Recorded [Member] | Consumer - Other [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	464		481
Unpaid Principal Balance	468		485
Related Allowance	(4)		(4)
Average Recorded Investment	491	497
Interest Income Recognized