Shareholders' Equity - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended
	Dec. 20, 2012	Oct. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	May 31, 2010
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Depositary shares issued during period, (in shares)		11,500
Preferred stock dividend rate		6.00%	6.00%
Proceeds from the issuance of preferred stock, net		$ 110,300,000	$ 110,337,000	$ 0	$ 0
Preferred stock liquidation preference (in dollars per share)			$ 10,000
Preferred stock depositary shares pro rata dividends declared	$ 146.67
Conversion price (in dollars per share)			$ 6
Conversion rate, convertible preferred stock into common			1,666.67
Premium for conversion price to concurrent common stock offering price			20.00%
Common stock offering price, new issue (in dollars per share)			$ 5.00
Conversion ratio into common stock if closing sale price exceed prior period conversion price			130.00%
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Issuance of common stock (in shares)		9,200,000
Proceeds from issuance of common stock		43,500,000
Common stock, shares authorized			128,000,000	128,000,000		128,000,000
Accumulated other comprehensive losses attributable to pension and postretirement benefit obligations, net of tax			1,000,000	1,100,000	900,000
Treasury stock (in shares)			218,320	223,886
Before Amendment
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, shares authorized						64,000,000
Accounts Payable and Accrued Liabilities
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Dividends Payable			$ 1,700,000