Capital and Regulatory Matters (Narrative) (Detail)			12 Months Ended
	Jan. 01, 2016	Feb. 15, 2013 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) quarter $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 shares	Jan. 01, 2019	Oct. 27, 2016 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Non-cumulative perpetual preferred stock			$ 144,500,000	$ 144,500,000
Non-cumulative perpetual preferred stock, dividend rate percentage			5.375%	5.375%
Additional Tier 1 Capital beyond Common Equity Tier 1			$ 0	$ 0
Corporation's aggregate subordinated notes			$ 136,127,000	$ 136,069,000
Preferred stock, shares issued | shares			6,000,000	6,000,000
Preferred stock, par value | $ / shares			$ 0.01	$ 0.01
Proceeds from issuance of preferred stock		$ 144,500,000
Accelerated share repurchase authorized amount				$ 100,000,000			$ 100,000,000
Stock repurchase program, period in force			2 years
Treasury stock, shares, acquired | shares			17,233	1,504,146	18,871
Aggregate dividends available for payment without prior regulatory approval			$ 489,100,000
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures | quarter			20
Two Thousand And Nineteen [Member] | Scenario, Forecast [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier One Risk Based Capital To Risk Weighted Assets Minimum Capital Required Basel III Phase In Schedule, Ratio						4.50%
Capital Conservation Buffer						2.50%
Minimum ratio of Tier 1 capital to risk-weighted assets						6.00%
Minimum ratio of Total capital to risk weighted assets						8.00%
Two Thousand And Nineteen [Member] | Scenario, Forecast [Member] | Minimum [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Effective common equity tier one capital to risk weighted assets, ratio upon full implementation						7.00%
Effective tier one capital ratio, upon full implementation						8.50%
Tier one risk based capital to risk weighted assets, ratio upon full implementation						10.50%
Minimum leverage ratio						4.00%
Two Thousand And Sixteen [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier one capital conservation buffer to risk weighted assets required under regulatory	0.625%
Tier one risk based capital conservation buffer initial requirements phasing duration	4 years
Series A Preferred Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Non-cumulative perpetual preferred stock, dividend rate percentage		5.375%
Preferred stock, shares issued | shares		6,000,000
Series A Preferred Stock, Liquidation preference value		$ 150,000,000	$ 25	$ 25
Preferred stock, par value | $ / shares		$ 0.01
Liquidation preference per share | $ / shares		$ 25
Treasury Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Treasury stock, shares, acquired | shares			0	1,485,493	0
Trust Preferred Securities Tier One Allowable Portion [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities			$ 33,300,000
Trust Preferred Securities Tier Two Capital Allowable Portion [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Trust preferred securities			133,000,000	$ 99,800,000
Floating Rate Subordinated Notes [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Permissible portion of subordinated note included in total capital				$ 20,000,000
Corporation's aggregate subordinated notes			$ 100,000,000
Per year percentage of decreases in permissible portion of Subordinate Note included in Total Capital			20.00%
Final years of the term of the notes			5 years