Mandatorily Redeemable Convertible Preferred Stock - Additional Information (Detail) (Preferred Stock Subject to Mandatory Redemption [Member], USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 28, 2006	Feb. 28, 2013
Preferred Stock Subject to Mandatory Redemption [Member]
Preferred Stock [Line Items]
Purchase of Series A convertible preferred stock	$ 125.0
Mandatory redeemable preferred stock price per share		$ 1,000
Dividend of Series A Convertible Preferred Stock		3.25%
Conversion of cumulative convertible preferred stock		125,000