Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
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	$ 2,365,093	$ 2,508,766
Interest bearing deposits with banks	299,097	463,022
Total investment securities held to maturity	1,764,181	1,657,950
Accrued interest receivable	53,303	52,375
Carrying Amount [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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	401,228	390,078
Interest bearing deposits with banks	299,097	463,022
Accrued interest receivable	53,303	52,375
Federal Reserve Bank and Federal Home Loan Bank stock	138,359	138,533
Deposits without stated maturities	8,877,529	8,755,252
Short-term borrowings	125,060	154,323
Accrued interest payable	16,766	15,917
Carrying Amount [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury securities [Member]
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	99,792	99,869
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member]
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	2,365,093	2,508,766
Long-term borrowings	2,695,897	2,697,299
Junior subordinated debentures issued to capital trusts	41,008	40,927
Total investment securities held to maturity	1,766,947	1,599,707
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member] | Obligations of states and political subdivisions [Member]
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	542,154	506,473
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member] | Residential mortgage-backed securities [Member]
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	969,341	813,647
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member] | Trust preferred securities [Member]
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	103,453	127,505
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate and other debt securities [Member]
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	52,207	52,213
Carrying Amount [Member] | Significant Unobservable Inputs (Level 3) [Member]
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	10,765,581	10,892,599
Fair Value [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
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	401,228	390,078
Interest bearing deposits with banks	299,097	463,022
Accrued interest receivable	53,303	52,375
Federal Reserve Bank and Federal Home Loan Bank stock	138,359	138,533
Deposits without stated maturities	8,877,529	8,755,252
Short-term borrowings	125,060	154,323
Accrued interest payable	16,766	15,917
Fair Value [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury securities [Member]
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	108,734	115,329
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]
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	2,404,271	2,563,726
Long-term borrowings	2,994,601	3,100,173
Junior subordinated debentures issued to capital trusts	42,731	40,776
Total investment securities held to maturity	1,764,181	1,657,950
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Obligations of states and political subdivisions [Member]
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	542,614	531,966
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Residential mortgage-backed securities [Member]
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	963,575	838,116
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Trust preferred securities [Member]
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	91,348	113,657
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate and other debt securities [Member]
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	57,910	58,882
Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]
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	$ 10,734,500	$ 10,908,742