Allowance for Loan Losses, Allowance for Losses on Lending-Related Commitments and Impaired Loans (Summary of Performance by Loan Class) (Detail) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		$ 17,446,413	$ 17,118,117	$ 14,953,059
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		17,356,914	17,034,060	14,871,287
Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		89,499	84,057	81,772
Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		4,890,246	4,713,909	4,211,932
Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		4,877,535	4,700,656	4,206,346
Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		12,711	13,253	5,586
Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		5,737,959	5,529,289	4,710,486
Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		5,709,703	5,502,644	4,680,504
Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		28,256	26,645	29,982
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		774,342	784,675	709,283
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		764,977	777,827	701,618
Home equity | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		9,365	6,848	7,665
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		626,043	607,451	495,925
Residential real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		614,079	595,408	481,677
Residential real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		11,964	12,043	14,248
Consumer and other
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		119,902	146,376	130,156
Consumer and other | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		119,238	145,963	129,829
Consumer and other | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		664	413	327
Commercial, industrial and other | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		3,404,555	3,258,528	2,807,752
Commercial, industrial and other | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		3,391,847	3,245,818	2,802,166
Commercial, industrial and other | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		12,708	12,710	5,586
Franchise | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		274,558	245,228	225,762
Franchise | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		274,558	245,228	225,762
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		193,735	222,806	186,372
Mortgage warehouse lines of credit | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		193,735	222,806	186,372
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
Asset-based lending | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		747,901	742,684	810,685
Asset-based lending | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		747,898	742,676	810,685
Asset-based lending | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		3	8	0
Leases | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		249,418	226,074	172,014
Leases | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		249,418	225,539	172,014
Leases | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		0	535	0
PCI - commercial | Commercial
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[1],[2]	20,079	18,589	9,347
PCI - commercial | Commercial | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[2]	20,079	18,589	9,347
PCI - commercial | Commercial | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[2]	0	0	0
Construction | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		391,322	358,660	256,827
Construction | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		391,049	358,354	256,827
Construction | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		273	306	0
Land | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		95,580	78,417	89,042
Land | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		93,834	76,666	86,396
Land | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		1,746	1,751	2,646
Office | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		888,494	863,001	743,126
Office | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		879,505	858,382	734,883
Office | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		8,989	4,619	8,243
Industrial | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		742,956	727,648	604,326
Industrial | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		731,996	718,084	600,830
Industrial | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		10,960	9,564	3,496
Retail | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		897,467	868,399	742,527
Retail | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		895,834	866,639	737,552
Retail | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		1,633	1,760	4,975
Multi-family | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		763,073	742,349	655,403
Multi-family | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		762,786	740,395	653,653
Multi-family | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		287	1,954	1,750
Mixed use and other | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		1,795,717	1,732,816	1,552,563
Mixed use and other | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		1,791,349	1,726,125	1,543,691
Mixed use and other | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		4,368	6,691	8,872
PCI - commercial real estate | Commercial real estate
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[1],[2]	163,350	157,999	66,672
PCI - commercial real estate | Commercial real estate | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[2]	163,350	157,999	66,672
PCI - commercial real estate | Commercial real estate | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[2]	0	0	0
Commercial insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		2,320,987	2,374,921	2,319,623
Commercial insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		2,296,089	2,350,066	2,295,659
Commercial insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		24,898	24,855	23,964
Life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		2,680,796	2,593,204	1,986,606
Life insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		2,679,155	2,593,204	1,986,606
Life insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans		1,641	0	0
PCI - life insurance loans | Premium finance receivables
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[1],[2]	296,138	368,292	389,048
PCI - life insurance loans | Premium finance receivables | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[2]	296,138	368,292	389,048
PCI - life insurance loans | Premium finance receivables | Non-performing
Financing Receivable, Recorded Investment [Line Items]
Loans, net of unearned income, excluding covered loans	[2]	$ 0	$ 0	$ 0

[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.