Loans (Narrative) (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Schedule Of Accretable Yield Activity Related to Loans Acquired With Evidence Of Credit Quality Deterioration Since Origination Table [Line Items]
Loans, net of unearned income	$ 31,402,903	$ 26,800,290	$ 25,304,659
Net deferred loan fees and costs and fair value accounting adjustments	(61,700)	9,100	5,600
Commercial
Schedule Of Accretable Yield Activity Related to Loans Acquired With Evidence Of Credit Quality Deterioration Since Origination Table [Line Items]
Loans, net of unearned income	11,859,232	8,285,920	8,270,774
Premium finance receivables
Schedule Of Accretable Yield Activity Related to Loans Acquired With Evidence Of Credit Quality Deterioration Since Origination Table [Line Items]
Unearned income portion of premium finance receivables	114,800	$ 118,400	$ 119,700
Commercial PPP Loans \| Commercial
Schedule Of Accretable Yield Activity Related to Loans Acquired With Evidence Of Credit Quality Deterioration Since Origination Table [Line Items]
Loans, net of unearned income	$ 3,300,000

Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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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.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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