Fair Value Measurement of Assets and Liabilities - Carrying Amounts and Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
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	$ 83,045	$ 134,915
Total investment securities held to maturity	1,816,049	1,711,427
Accrued interest receivable	54,286	53,964
Deposits with stated maturities	2,112,517	2,179,269
Carrying Amount [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	1,813,096	1,731,737
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	296,557	234,253
Interest bearing deposits with banks	83,045	134,915
Accrued interest receivable	54,286	53,964
Federal Reserve Bank and Federal Home Loan Bank stock	141,734	137,234
Deposits without stated maturities	9,155,468	9,139,993
Short-term borrowings	537,110	281,455
Accrued interest payable	13,323	16,442
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	139,227	139,255
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	2,112,517	2,179,269
Long-term borrowings	2,795,239	2,792,306
Junior subordinated debentures issued to capital trusts	41,130	41,089
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Agency 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	14,454	4,427
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	531,931	545,886
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	971,361	886,043
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	98,450	103,458
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	57,673	52,668
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	11,587,885	11,453,995
Fair Value [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	1,816,049	1,711,427
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	296,557	234,253
Interest bearing deposits with banks	83,045	134,915
Accrued interest receivable	54,286	53,964
Federal Reserve Bank and Federal Home Loan Bank stock	141,734	137,234
Deposits without stated maturities	9,155,468	9,139,993
Short-term borrowings	537,110	281,455
Accrued interest payable	13,323	16,442
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	146,896	144,307
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	2,139,016	2,206,427
Long-term borrowings	3,037,960	3,036,953
Junior subordinated debentures issued to capital trusts	45,228	45,261
Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Government Agency 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	14,488	4,365
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	539,658	543,151
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	966,050	871,021
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	86,435	91,489
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	62,522	57,094
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	$ 11,411,963	$ 11,294,348