Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Impaired Loans by Loan Class) (Detail) (USD $)	3 Months Ended				12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	$ 48,610,000	[1]	$ 86,381,000	[1]	$ 69,487,000	[1]
Impaired Financing Receivable, Related Allowance	6,199,000		8,197,000		6,270,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	63,794,000		56,596,000		57,925,000
Impaired Financing Receivable, Recorded Investment	112,404,000	[2]	142,977,000	[2]	127,412,000	[2]
Impaired Financing Receivable, Unpaid Principal Balance	136,169,000		168,203,000		153,742,000
Impaired Financing Receivable, Average Recorded Investment	113,693,000		145,257,000		134,967,000
Impaired Financing Receivable, Interest Income Recognized	1,588,000		1,915,000		7,190,000
Commercial | Commercial and industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,230,000		9,167,000		9,989,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	7,830,000		10,029,000		10,785,000
Impaired Financing Receivable, Related Allowance	1,795,000		2,459,000		1,915,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	7,465,000		9,340,000		10,784,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	92,000		120,000		539,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,630,000		7,789,000		5,797,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	7,595,000		14,415,000		8,862,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,647,000		8,179,000		6,664,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	125,000		208,000		595,000
Commercial | Franchise
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial | Mortgage warehouse lines of credit
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial | Community Advanatage - homeowners association
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial | Aircraft
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial | Asset-based lending
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		670,000		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		2,465,000		0
Impaired Financing Receivable, Related Allowance	0		620,000		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		677,000		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		31,000		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		25,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		1,952,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		87,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		100,000
Commercial | Tax exempt
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial | Leases
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial | Other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Commercial real-estate | Residential construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		891,000		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		891,000		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		1,245,000		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		12,000		0
Commercial real-estate | Commercial construction
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		3,099,000		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		3,099,000		0
Impaired Financing Receivable, Related Allowance	0		24,000		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		3,099,000		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		28,000		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,645,000		1,466,000		2,875,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,645,000		1,471,000		3,085,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,645,000		1,418,000		3,183,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	30,000		17,000		151,000
Commercial real-estate | Land
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	4,475,000		9,260,000		5,011,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	8,090,000		9,625,000		8,626,000
Impaired Financing Receivable, Related Allowance	29,000		174,000		43,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	4,734,000		9,688,000		5,933,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	127,000		79,000		544,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,134,000		4,982,000		10,210,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,868,000		8,764,000		10,941,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,137,000		4,985,000		10,268,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	62,000		109,000		430,000
Commercial real-estate | Office
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	8,354,000		8,712,000		11,038,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	11,053,000		9,398,000		12,863,000
Impaired Financing Receivable, Related Allowance	598,000		1,069,000		305,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	8,399,000		8,767,000		11,567,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	131,000		90,000		576,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	6,890,000		6,260,000		4,132,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	6,965,000		6,301,000		5,020,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	6,971,000		6,266,000		4,445,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	77,000		83,000		216,000
Commercial real-estate | Industrial
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	1,402,000		6,597,000		195,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	1,487,000		6,765,000		277,000
Impaired Financing Receivable, Related Allowance	559,000		513,000		15,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,406,000		5,985,000		214,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	20,000		81,000		13,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,772,000		2,298,000		4,160,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	3,134,000		2,470,000		4,498,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,837,000		2,314,000		3,807,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	55,000		47,000		286,000
Commercial real-estate | Retail
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	10,259,000		12,763,000		11,045,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	12,286,000		12,903,000		14,566,000
Impaired Financing Receivable, Related Allowance	371,000		826,000		487,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	10,294,000		12,819,000		12,116,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	128,000		132,000		606,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,053,000		10,419,000		5,487,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	9,130,000		12,273,000		7,470,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,315,000		11,006,000		6,915,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	105,000		140,000		330,000
Commercial real-estate | Multi-family
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,266,000		2,053,000		2,808,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,363,000		2,143,000		3,321,000
Impaired Financing Receivable, Related Allowance	241,000		122,000		158,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,273,000		2,057,000		2,839,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	26,000		23,000		145,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	777,000		1,078,000		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,199,000		2,013,000		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	778,000		1,201,000		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	13,000		23,000		0
Commercial real-estate | Mixed use and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	7,891,000		25,420,000		21,777,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	10,041,000		25,591,000		24,076,000
Impaired Financing Receivable, Related Allowance	1,449,000		1,272,000		2,240,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	7,907,000		25,853,000		21,483,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	116,000		291,000		1,017,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	17,479,000		3,161,000		7,985,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	17,723,000		5,044,000		8,804,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	17,688,000		3,096,000		9,533,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	185,000		67,000		449,000
Home equity
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,807,000		2,109,000		1,946,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,962,000		2,534,000		2,055,000
Impaired Financing Receivable, Related Allowance	948,000		596,000		475,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,809,000		2,117,000		1,995,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	29,000		24,000		80,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	5,072,000		5,428,000		4,453,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	6,771,000		7,044,000		6,172,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	5,126,000		5,777,000		4,666,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	70,000		73,000		256,000
Residential real-estate
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	3,728,000		6,222,000		5,467,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	3,934,000		6,362,000		5,600,000
Impaired Financing Receivable, Related Allowance	183,000		427,000		606,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	3,724,000		6,094,000		5,399,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	45,000		68,000		241,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	13,159,000		11,541,000		12,640,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	14,644,000		14,427,000		14,334,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	13,190,000		11,699,000		12,682,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	145,000		137,000		595,000
Premium finance receivables | Commercial insurance loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Premium finance receivables | Life insurance loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Premium finance receivables | PCI - life insurance loans
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, Related Allowance	0		0		0
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	0		0		0
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		0
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0		0		0
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	0		0		0
Consumer and other
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, with Related Allowance, Recorded Investment	198,000		309,000		211,000
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	200,000		367,000		213,000
Impaired Financing Receivable, Related Allowance	26,000		95,000		26,000
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	203,000		290,000		214,000
Impaired Financing Receivable, with Related Allowance, Interest Income Recognized	4,000		5,000		10,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	183,000		1,283,000		161,000
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	249,000		1,809,000		222,000
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	145,000		1,285,000		173,000
Impaired Financing Receivable, with No Related Allowance, Interest Income Recognized	$ 3,000		$ 27,000		$ 11,000

[1] These impaired loans require an allowance for loan losses because the estimated fair value of the loans or related collateral is less than the recorded investment in the loans.

[2] Impaired loans are considered by the Company to be non-accrual loans, TDRs or loans with principal and/or interest at risk, even if the loan is current with all payments of principal and interest.