Preferred Stock - Additional Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Mar. 31, 2015	Dec. 30, 2013
Auction Market Preferred Securities, Stock Series [Line Items]
Preferred Stock, shares authorized			10,000,000
Preferred Stock, par value per share	$ 0.01		$ 0.01
Preferred Stock, Shares Authorized	9,765,900		9,945,539
Preferred Stock, Shares Issued	0		0
Preferred Stock Redeemed	375
6.75% Series C Cumulative Redeemable Perpetual Preferred Stock
Auction Market Preferred Securities, Stock Series [Line Items]
Preferred Stock, par value per share	$ 0.01		$ 0.01
Preferred Stock, Shares Authorized	54,461		54,461
Preferred Stock, Shares Issued	54,458		54,458
Preferred Stock, Dividend Rate, Percentage	6.75%
Cumulative Series D 6% Non-Qualified Preferred Stock
Auction Market Preferred Securities, Stock Series [Line Items]
Preferred Stock, Shares Authorized		179,764		179,639
Preferred Stock, Shares Issued	125				125
Preferred Stock, Dividend Rate, Percentage		6.00%
Preferred Stock, Liquidation Preference Per Share					$ 1,000
Cumulative Series E Eighteen Point Seven Five Percent Nonvoting Preferred Stock [Member]
Auction Market Preferred Securities, Stock Series [Line Items]
Preferred Stock, Shares Issued	250				250
Preferred Stock, Dividend Rate, Percentage		18.75%
Preferred Stock, Liquidation Preference Per Share					$ 1,000