Stockholders' Equity - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended		3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Net Share Settlements	Dec. 31, 2012 Net Share Settlements	Dec. 31, 2012 Restricted Stock	Mar. 31, 2013 Three-Year Period Restricted Stock	Mar. 31, 2012 Three-Year Period Restricted Stock	Mar. 31, 2013 Four-Year Period Restricted Stock	Mar. 31, 2012 Four-Year Period Restricted Stock
Class of Stock [Line Items]
Common stock, shares authorized	80,000,000	80,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock issued from treasury stock	34,175	133,200
Issued common stock for the exercise of stock options		0
Restricted shares of common stock granted						432,400	646,438	262,000	179,000
Restricted shares of common stock vesting period, (in years)					3 years	3 years	3 years	4 years	4 years
Restricted stock granted	1,042,281				42,513
Percentage of target number of shares					25.00%
Treasury shares acquired, shares			251,519	357,714
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares issued
Preferred stock, shares outstanding	0	0