Common Stock and Other Equity Related Transactions - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
Common Stock
Class of Stock [Line Items]
Dividends Payable, Date to be Paid	Apr. 12, 2013
Common Stock, Dividends, Per Share, Cash Paid	$ 0.50
Dividends Payable, Date of Record	Mar. 28, 2013
Cumulative Series C Six Point Seven Five Percent Redeemable Perpetual Preferred Stock [Member]
Class of Stock [Line Items]
Dividends Payable, Date to be Paid	Apr. 01, 2013
Preferred Stock, Dividends, Per Share, Cash Paid	$ 0.421875
Dividends Payable, Date of Record	Mar. 21, 2013