Shareholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Auction Market Preferred Securities, Stock Series [Line Items]
Common stock par value	$ 1	$ 1	$ 1
Dividend description	The Company may only declare and pay dividends on common stock (or repurchase shares of common stock) if, after payment of such dividend, the dollar amount of Tier 1 capital would be at least 90% of Tier 1 capital as of August 4, 2011, excluding charge-offs and redemptions of the Series D preferred stock (Tier 1 dividend threshold)
Minimum rate required to declare dividend	90.00%
Expected dividend rate	1.00%
Percentage of redemption price	100.00%
Series C Preferred Stock [Member]
Auction Market Preferred Securities, Stock Series [Line Items]
Convertible preferred stock shares converted	551,858	763,378
Convertible perpetual preferred stock			$ 20.6
Preferred stock aggregate liquidation	20.6
Series D Preferred Stock [Member]
Auction Market Preferred Securities, Stock Series [Line Items]
Convertible perpetual preferred stock			37.9
Preferred stock aggregate liquidation	$ 37.9