Loans (Summary of Loan Portfolio) (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 15,513,650	$ 14,409,398	$ 13,749,996
Covered loans	193,410	226,709	275,154
Total loans	$ 15,707,060	$ 14,636,107	$ 14,025,150
Total loans, net of unearned income, excluding covered loans, percentage	99.00%	98.00%	98.00%
Covered loans, percentage	1.00%	2.00%	2.00%
Total loans, percentage	100.00%	100.00%	100.00%
Commercial
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 4,330,344	$ 3,924,394	$ 3,640,430
Total loans, net of unearned income, excluding covered loans, percentage	27.00%	26.00%	26.00%
Commercial real estate
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 4,850,590	$ 4,505,753	$ 4,353,472
Total loans, net of unearned income, excluding covered loans, percentage	31.00%	31.00%	31.00%
Home equity
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 712,350	$ 716,293	$ 713,642
Total loans, net of unearned income, excluding covered loans, percentage	5.00%	5.00%	5.00%
Residential real estate
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 503,015	$ 483,542	$ 451,905
Total loans, net of unearned income, excluding covered loans, percentage	3.00%	3.00%	3.00%
Consumer and other
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 119,468	$ 151,012	$ 160,373
Total loans, net of unearned income, excluding covered loans, percentage	1.00%	1.00%	1.00%
Commercial insurance loans \| Premium finance receivables
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 2,460,408	$ 2,350,833	$ 2,378,529
Total loans, net of unearned income, excluding covered loans, percentage	16.00%	16.00%	17.00%
Life insurance \| Premium finance receivables
Loans [Line Items]
Loans, net of unearned income, excluding covered loans	$ 2,537,475	$ 2,277,571	$ 2,051,645
Total loans, net of unearned income, excluding covered loans, percentage	16.00%	16.00%	15.00%

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5074-111524

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