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 Performance by Loan Class) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	$ 14,953,059		$ 14,409,398		$ 13,133,160
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	14,871,287		14,330,721		13,043,036
Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	81,772		78,677		90,124
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,211,932		3,924,394		3,439,197
Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,206,346		3,914,763		3,427,028
Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,586		9,631		12,169
Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,710,486		4,505,753		4,262,255
Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,680,504		4,479,148		4,228,522
Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	29,982		26,605		33,733
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	709,283		716,293		707,748
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	701,618		710,119		700,437
Home equity | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	7,665		6,174		7,311
Residential real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	495,925		483,542		426,769
Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,319,623		2,350,833		2,208,361
Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	130,156		151,012		159,496
Consumer and other | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	129,829		150,617		158,295
Consumer and other | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	327		395		1,201
Commercial and industrial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,484,465		2,233,364		1,995,309
Commercial and industrial | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,478,879		2,223,758		1,983,810
Commercial and industrial | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	5,586		9,606		11,499
Franchise | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	225,762		233,316		221,101
Franchise | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	225,762		233,316		221,101
Franchise | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Mortgage warehouse lines of credit | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	186,372		139,003		60,809
Mortgage warehouse lines of credit | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	186,372		139,003		60,809
Mortgage warehouse lines of credit | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Community Advanatage - homeowners association | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	108,382		106,364		91,414
Community Advanatage - homeowners association | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	108,382		106,364		91,414
Community Advanatage - homeowners association | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Aircraft | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,975		8,065		8,840
Aircraft | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	6,975		8,065		8,840
Aircraft | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Asset-based lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	810,685		806,402		740,668
Asset-based lending | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	810,685		806,377		739,998
Asset-based lending | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		25		670
Tax exempt | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	205,195		217,487		177,973
Tax exempt | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	205,195		217,487		177,973
Tax exempt | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Leases | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	172,014		160,136		121,986
Leases | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	172,014		160,136		121,986
Leases | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Other | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,735		11,034		10,261
Other | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,735		11,034		10,261
Other | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
PCI - commercial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	9,347	[1],[2]	9,223	[1],[2]	10,836	[1],[2]
PCI - commercial | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	9,347	[2]	9,223	[2]	10,836	[2]
PCI - commercial | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	[2]	0	[2]	0	[2]
Residential construction | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	46,796		38,696		36,397
Residential construction | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	46,796		38,696		36,397
Residential construction | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
Commercial construction | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	210,031		187,766		151,630
Commercial construction | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	210,031		187,536		150,786
Commercial construction | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		230		844
Land | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	89,042		91,830		107,970
Land | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	86,396		89,174		105,565
Land | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,646		2,656		2,405
Office | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	743,126		705,432		651,165
Office | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	734,883		698,144		644,195
Office | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	8,243		7,288		6,970
Industrial | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	604,326		623,970		625,060
Industrial | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	600,830		621,578		618,959
Industrial | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	3,496		2,392		6,101
Retail | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	742,527		731,488		677,430
Retail | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	737,552		727,336		667,890
Retail | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	4,975		4,152		9,540
Multi-family | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	655,403		605,742		575,763
Multi-family | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	653,653		605,493		574,436
Multi-family | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,750		249		1,327
Mixed use and other | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,552,563		1,465,117		1,361,236
Mixed use and other | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,543,691		1,455,479		1,354,690
Mixed use and other | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	8,872		9,638		6,546
PCI - commercial real estate | Commercial real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	66,672	[1],[2]	55,712	[1],[2]	75,604	[1],[2]
PCI - commercial real estate | Commercial real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	66,672	[2]	55,712	[2]	75,604	[2]
PCI - commercial real estate | Commercial real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	[2]	0	[2]	0	[2]
Residential real estate | Residential real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	493,562		481,308		423,694
Residential real estate | Residential real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	479,314		465,806		409,309
Residential real estate | Residential real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	14,248		15,502		14,385
PCI - residential real estate | Residential real-estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,363	[1],[2]	2,234	[1],[2]	3,075	[1],[2]
PCI - residential real estate | Residential real-estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,363	[2]	2,234	[2]	3,075	[2]
PCI - residential real estate | Residential real-estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0	[2]	0	[2]	0	[2]
Commercial insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,319,623		2,350,833		2,208,361
Commercial insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	2,295,659		2,330,463		2,187,036
Commercial insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	23,964		20,370		21,325
Life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,986,606		1,884,092		1,516,132
Life insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	1,986,606		1,884,092		1,516,132
Life insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	0		0		0
PCI - life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	389,048	[1],[2]	393,479	[1],[2]	413,202	[1],[2]
PCI - life insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	389,048	[2]	393,479	[2]	413,202	[2]
PCI - life insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	$ 0	[2]	$ 0	[2]	$ 0	[2]

[1] PCI loans represent loans acquired with evidence of credit quality deterioration since origination, in accordance with ASC 310-30. Loan agings are based upon contractually required payments.

[2] PCI loans represent loans acquired with evidence of credit quality deterioration since origination, in accordance with ASC 310-30. See Note 6 - Loans for further discussion of these purchased loans.