Capital and Regulatory Matters - Additional Information (Detail) (USD $)	1 Months Ended		6 Months Ended			6 Months Ended	12 Months Ended	1 Months Ended		1 Months Ended
	Aug. 31, 2013	Feb. 28, 2013	Jun. 30, 2014 quarter	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Floating Rate Subordinated Notes [Member]	Dec. 31, 2013 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, 2014 Series A Preferred Stock [Member]	Dec. 31, 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			$ 144,500,000
Preferred stock dividend rate percentage			5.375%							5.375%
Trust preferred securities			133,000,000
Corporation's aggregate subordinated notes			137,115,000		123,712,000	100,000,000
Per Year Percentage decrease in permissible portion of subordinate note included in Total Capital						20.00%
Final years of the term of the notes						5 years
Permissible portion of subordinated note included in total capital						40,000,000	60,000,000
Preferred stock shares issued			6,000,000		6,000,000				6,000,000
Preferred stock aggregate liquidation preference value									150,000,000			25	25
Preferred stock, par value			$ 0.01		$ 0.01						$ 0.01
Preferred stock liquidation preference per share														$ 25
Net proceeds from the issuance and sale of the Preferred Stock			0	144,486,000				144,500,000
Accelerated share repurchase program repurchase amount		144,000,000
Accelerated share repurchase program repurchase share	331,671	1,905,077
Accelerated share repurchase program repurchase share percent		80.00%
Stock repurchase program authorized amount			150,000,000
Maximum dividends available without prior regulatory approval			$ 272,000,000
Maximum number of quarterly periods by which the corporation has the right to defer interest payments on junior subordinated deferrable interest debentures			20
Minimum number of days to be considered past due			90 days