Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended						9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Series K Cumulative Redeemable Preferred Stock [Member]	Sep. 30, 2013 Series J Cumulative Redeemable Preferred Stock [Member]	Sep. 30, 2013 ATM [Member]	Mar. 01, 2012 ATM [Member]	Sep. 30, 2013 Restricted Stock [Member]	Sep. 30, 2013 LTIP Unit Awards	Sep. 30, 2013 Series F Preferred Stock [Member]	Sep. 30, 2013 Noncontrolling Interest	Sep. 30, 2012 Noncontrolling Interest
Class of Stock [Line Items]
Depositary shares redeemed					2,000,000	4,000,000
Payments for repurchase of redeemable preferred stock			$ 150,000	$ 0
Portion of preferred stock					0.0001	0.0001
Dividend rate per share					7.25%	7.25%
Par value of each depositary share					$ 0.01	$ 0.01
Redemption price per share					$ 25.00	$ 25.00
Preferred dividend per depositary share					$ 0.090625	$ 0.055382
Total preferred dividend, depositary shares					181	221
Cost associated with share redemption	2,121	0	5,667	0	2,121	3,546
Underwritten public offering shares			8,400,000
Net proceeds from underwriting			132,050
Shares of common stock issuable under at-the-market offering								12,500,000
Common stock issued under at-the-market offering							2,315,704
Aggregate gross sale proceeds								125,000
Proceeds from the issuance of common stock			174,081	134,905			41,735
Noncontrolling interest reclassified to equity			0	0								943	2,710
Conversion of units to common stock			99,508
Restricted stock/unit awards to employees									284,461	718,960
Fair value of Long Term Incentive Program unit awards										5,411
Minimum Percentage Of Shares Obtainable Under Long Term Incentive Program										0.00%
Maximum Percentage Of Shares Obtainable Under Long Term Incentive Program										100.00%
Fair value of restricted stock/unit awards									4,719
Vesting period of restricted stock/unit awards to employees									3 years
Compensation expense related to restricted shares issued during the quarter			1,008
Amortization related to restricted stock and unit awards	1,769	1,309	4,436	3,707
Amount of share based compensation expense capitalized	15	19	32	19
Unrecognized compensation expense related to restricted stock/unit awards	$ 9,094		$ 9,094
Weighted average period during which unrecognized compensation expense is expected to be recognized			0 years 10 months 26 days
Minimum fixed coupon rate of preferred stock											2.375%
Number of years of U.S. treasury rate one											30 years
Number of years of U.S. treasury rate two											10 years
LIBOR rate											3 month LIBOR
New coupon rate of preferred stock											5.935%