Capital and Regulatory Matters - Additional Information (Detail) (USD $)	1 Months Ended	6 Months Ended													6 Months Ended						6 Months Ended			6 Months Ended		12 Months Ended	1 Months Ended		1 Months Ended
	Feb. 28, 2013	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 OTC Derivatives [Member]	Jun. 30, 2013 Basel I [Member] Category	Jun. 30, 2013 Basel I [Member] Risk Weighting Category One [Member]	Jun. 30, 2013 Basel I [Member] Risk Weighting Category Two [Member]	Jun. 30, 2013 Basel I [Member] Risk Weighting Category Three [Member]	Jun. 30, 2013 Basel I [Member] Risk Weighting Category Four [Member]	Jun. 30, 2013 Commercial Real Estate Acquisition, Development and Construction Loans [Member]	Jun. 30, 2013 As Amended [Member] Commercial Real Estate Acquisition, Development and Construction Loans [Member]	Jun. 30, 2013 Scenario, Forecast [Member]	Jun. 30, 2013 Scenario, Forecast [Member] Minimum [Member]	Jun. 30, 2013 Scenario, Forecast [Member] Banking [Member] Minimum [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Basel III [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Securities Lending Transactions [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Claims on Securities Firms [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Minimum [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Minimum [Member] Basel III [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Maximum [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Maximum [Member] Basel III [Member]	Jun. 30, 2013 2015 [Member] Scenario, Forecast [Member] Other Residential Mortgages [Member]	Jun. 30, 2013 2016 [Member] Scenario, Forecast [Member]	Jun. 30, 2013 Floating Rate Subordinated Notes [Member]	Dec. 31, 2012 Floating Rate Subordinated Notes [Member]	Feb. 28, 2013 Non-Cumulative Perpetual Preferred Stock and Series A Preferred Stock [Member]	Feb. 15, 2013 Non-Cumulative Perpetual Preferred Stock and Series A Preferred Stock [Member]	Feb. 28, 2013 Non-Cumulative Perpetual Preferred Stock [Member]	Feb. 15, 2013 Non-Cumulative Perpetual Preferred Stock [Member]	Jun. 30, 2013 Series A Preferred Stock [Member]	Feb. 15, 2013 Series A Preferred Stock [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Preferred stock value issued include for regulatory tier one capital calculations		$ 144,700,000
Preferred stock dividend rate percentage		5.375%																											5.375%
Corporation's aggregate subordinated notes		123,712,000	123,712,000																						100,000,000
Trust preferred securities		120,000,000
Percentage of decreases in permissible portion																									20.00%
Permissible portion of subordinated note included in capital																									60,000,000	80,000,000
Preferred stock shares issued		6,000,000	0																									6,000,000
Preferred stock liquidation preference value																												150,000,000			25
Preferred stock liquidation preference		$ 0.01	$ 0.01																											$ 0.01
Preferred stock liquidation preference																																$ 25
Net proceeds from the issuance and sale of the Preferred Stock		144,486,000																									144,500,000
Accelerated share repurchase program repurchase amount	144,000,000
Accelerated share repurchase program repurchase share	1,900,000
Accelerated share repurchase program repurchase share percent	80.00%
Stock repurchase program authorized amount		150,000,000
Maximum dividends available without prior regulatory approval		$ 243,300,000
Minimum ratio of CET1 to risk-weighted assets															4.50%
Capital conservation buffer															2.50%
Minimum ratio of CET1 to risk-weighted assets																			7.00%
Minimum ratio of Tier 1 capital to risk-weighted assets															6.00%
Minimum ratio of Total capital to risk-weighted assets															8.00%
Tier 1 capital ratio																			8.50%
Minimum ratio of Total capital to risk-weighted assets																			10.50%
Minimum leverage ratio													4.00%	3.00%
Threshold of items deducted from CET1															10.00%
Threshold of Aggregate items deducted from CET1															15.00%
Implementation of the deductions and other adjustments to CET1, Percentage															40.00%
Trust preferred Securities															25.00%									0.00%
Implementation of the deductions and other adjustments to CET1															4 years
Implementation of the deductions and other adjustments to CET1, Additional Percentage												20.00%
Implementation of the capital conservation buffer, Percentage																								0.625%
Capital conservation buffer period																								4 years
Required CET1 ratio for well-capitalized status as per Basel III Capital Rules															6.50%
Minimum Tier 1 capital ratio for well-capitalized status		6.00%																	8.00%
Leverage ratio required for adequately capitalized															3.00%
Number of risk-weighting categories					4
Risk weightings percentage						0.00%	20.00%	50.00%	100.00%	100.00%	150.00%						20.00%	100.00%		0.00%		600.00%	150.00%
Credit conversion factor		0.00%														20.00%
Original maturity period																					1 year
Current cap on risk weight for derivatives				50.00%