Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Interest bearing deposits with banks	$ 111,283	$ 171,710
Total investment securities held to maturity	1,904,523	1,924,597
Accrued interest receivable	68,245	66,816
Deposits with stated maturities	3,215,094	3,138,871
Carrying Amount
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	1,902,329	1,925,572
Carrying Amount | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Cash and due from banks	225,443	220,791
Interest bearing deposits with banks	111,283	171,710
Accrued interest receivable	68,245	66,816
Federal Reserve Bank and Federal Home Loan Bank stock	188,557	147,127
Deposits without stated maturities	14,116,047	14,591,837
Short-term borrowings	1,644,964	1,080,960
Accrued interest payable	9,473	10,675
Carrying Amount | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	138,793	138,830
Carrying Amount | Significant Other Observable Inputs (Level 2)
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Deposits with stated maturities	3,215,094	3,138,871
Long-term borrowings	1,634,008	1,433,906
Junior subordinated debentures issued to capital trusts	41,617	41,577
Carrying Amount | Significant Other Observable Inputs (Level 2) | U.S. government agency securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	10,722	11,329
Carrying Amount | Significant Other Observable Inputs (Level 2) | Obligations of states and political subdivisions
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	538,032	566,590
Carrying Amount | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	1,113,413	1,112,460
Carrying Amount | Significant Other Observable Inputs (Level 2) | Trust preferred securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	59,810	59,804
Carrying Amount | Significant Other Observable Inputs (Level 2) | Corporate and other debt securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	41,559	36,559
Carrying Amount | Significant Unobservable Inputs (Level 3)
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Net loans	17,334,055	17,121,684
Fair Value
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	1,904,523	1,924,597
Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Cash and due from banks	225,443	220,791
Interest bearing deposits with banks	111,283	171,710
Accrued interest receivable	68,245	66,816
Federal Reserve Bank and Federal Home Loan Bank stock	188,557	147,127
Deposits without stated maturities	14,116,047	14,591,837
Short-term borrowings	1,648,547	1,081,751
Accrued interest payable	9,473	10,675
Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	147,419	147,495
Fair Value | Significant Other Observable Inputs (Level 2)
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Deposits with stated maturities	3,235,676	3,160,572
Long-term borrowings	1,723,673	1,523,386
Junior subordinated debentures issued to capital trusts	46,084	45,785
Fair Value | Significant Other Observable Inputs (Level 2) | U.S. government agency securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	10,881	11,464
Fair Value | Significant Other Observable Inputs (Level 2) | Obligations of states and political subdivisions
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	551,788	577,826
Fair Value | Significant Other Observable Inputs (Level 2) | Residential mortgage-backed securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	1,103,770	1,102,802
Fair Value | Significant Other Observable Inputs (Level 2) | Trust preferred securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	48,034	47,290
Fair Value | Significant Other Observable Inputs (Level 2) | Corporate and other debt securities
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Total investment securities held to maturity	42,631	37,720
Fair Value | Significant Unobservable Inputs (Level 3)
Fair value and carrying amounts of assets and liabilities not measured and not reported at fair value on the consolidated statement of financial condition
Net loans	$ 16,961,749	$ 16,756,655