Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended			9 Months Ended			9 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Series F Preferred Stock	Mar. 06, 2014 Series F Preferred Stock	Sep. 30, 2014 Series F Preferred Stock Minimum	Sep. 30, 2014 Series G Preferred Stock	Mar. 31, 2014 Series G Preferred Stock	Sep. 30, 2014 Convertible Common Stock	Sep. 30, 2013 Convertible Common Stock
Class of Stock [Line Items]
Depositary shares redeemed							50,000			25,000
Depositary share percentage per share							1.00%			1.00%
Dividend rate per share						6.236%			7.236%
Preferred stock, par value per share							$ 0.01			$ 0.01
Redemption price per share							$ 1,000.00			$ 1,000.00
Dividend per share						$ 11.3299			$ 36.18
Total dividend						$ 566			$ 905
Cost associated with share redemption	0	2,121	1,462	5,667
Preferred stock shares authorized	10,000,000		10,000,000
Preferred stock, shares outstanding	0		0		750
Fixed coupon rate of preferred stock								2.375%
Number of years of US treasury rate one						30 years
Number of years of US treasury rate two						10 years
LIBOR rate						3-month LIBOR
New coupon rate of preferred stock						6.275%
Units converted into common stock											175,333	99,508
Noncontrolling interest reclassified to stockholders' equity			$ 0	$ 0							$ 1,697	$ 943