Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
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	$ 92,975	$ 170,225
Total investment securities held to maturity	1,803,711	1,621,039
Accrued interest receivable	65,193	63,554
Deposits with stated maturities	3,064,636	3,157,904
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	1,765,220	1,596,385
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	220,156	243,575
Interest bearing deposits with banks	92,975	170,225
Accrued interest receivable	65,193	63,554
Federal Reserve Bank and Federal Home Loan Bank stock	161,684	145,068
Deposits without stated maturities	13,291,422	13,095,647
Short-term borrowings	1,411,844	1,076,991
Accrued interest payable	11,434	13,110
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	138,904	138,978
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	3,064,636	3,157,904
Long-term borrowings	1,545,495	1,810,728
Junior subordinated debentures issued to capital trusts	41,496	41,414
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	12,076	12,859
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	565,509	504,865
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	957,377	852,289
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	59,795	59,785
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	31,559	27,609
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	16,391,092	15,936,929
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	1,803,711	1,621,039
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	220,156	243,575
Interest bearing deposits with banks	92,975	170,225
Accrued interest receivable	65,193	63,554
Federal Reserve Bank and Federal Home Loan Bank stock	161,684	145,068
Deposits without stated maturities	13,291,422	13,095,647
Short-term borrowings	1,411,844	1,076,991
Accrued interest payable	11,434	13,110
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	152,772	149,483
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	3,103,627	3,203,389
Long-term borrowings	1,716,189	1,945,741
Junior subordinated debentures issued to capital trusts	43,865	44,127
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	12,563	13,130
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	591,925	527,263
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	967,142	855,272
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	46,030	46,437
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	33,279	29,454
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	$ 16,410,318	$ 15,824,475