Partners' Capital - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended						0 Months Ended		3 Months Ended		12 Months Ended			12 Months Ended						3 Months Ended	12 Months Ended				12 Months Ended					12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Series G Preferred Units [Member]	Dec. 31, 2012 Series G Preferred Units [Member]	May 27, 2004 Series G Preferred Units [Member]	Apr. 11, 2013 Series J Preferred Units [Member]	Dec. 21, 2012 Series J Preferred Units [Member]	Jun. 30, 2013 Series J Preferred Units [Member]	Dec. 31, 2012 Series J Preferred Units [Member]	Dec. 31, 2013 Series J Preferred Units [Member]	Dec. 31, 2012 Series J Preferred Units [Member]	Jan. 13, 2006 Series J Preferred Units [Member]	Dec. 31, 2013 Common Stock [Member]	Dec. 31, 2012 Common Stock [Member]	Dec. 31, 2011 Common Stock [Member]	Dec. 31, 2013 Series F Preferred Units [Member]	Dec. 31, 2012 Series F Preferred Units [Member]	May 27, 2004 Series F Preferred Units [Member]	Sep. 30, 2013 Series K Preferred Units [Member]	Dec. 31, 2013 Series K Preferred Units [Member]	Jul. 18, 2013 Series K Preferred Units [Member]	Dec. 31, 2012 Series K Preferred Units [Member]	Aug. 21, 2006 Series K Preferred Units [Member]	Dec. 31, 2013 Atm [Member]	Dec. 31, 2012 Atm [Member]	Dec. 31, 2011 Atm [Member]	Mar. 01, 2012 Atm [Member] Maximum Common Stock [Member]	Feb. 28, 2011 Atm [Member] Maximum Common Stock [Member]	Dec. 31, 2013 Scenario, Forecast [Member] Series G Preferred Units [Member]
Class of Stock [Line Items]
Operating Partnership, aggregate cash payment									$ 80,223
Operating Partnership, shares									4,597,313
Liquidation Preference	75,000				225,000				75,000	225,000		25,000	25,000					100,000		100,000					50,000	50,000					50,000
Issue date of depositary shares												May 27, 2004							Jan. 13, 2006						May 27, 2004				Aug. 21, 2006									Mar. 31, 2014
Depositary shares issued														25,000							6,000,000						50,000					2,000,000
Depositary share percentage per share														$ 0.0100							$ 0.0001						$ 0.0100					$ 0.0001
Par value per depositary shares														$ 0.01							$ 0.01						$ 0.01					$ 0.01
Initial offering price per depositary share														$ 1,000							$ 25.00						$ 1,000					$ 25.00
Dividend rate per share												7.236%							7.25%						6.236%				7.25%
Minimum fixed coupon rate of preferred stock																									2.375%
Number of years of U.S treasury rate one												30 years													30 years
Number of years of U.S treasury rate two												10 years													10 years
LIBOR rate												3-month LIBOR													3-month LIBOR
New coupon rate of preferred stock																									6.065%
Aggregate redemption price																					150,000								50,000
Redemption price per depositary share												$ 1,000			$ 25.00	$ 25.00			$ 25.00						$ 1,000				$ 25.00	$ 25.00
Dividend equivalent to per depositary share												$ 72.36
Floating rates during floating rate periods												2.50%
Depositary Shares redeemed															4,000,000	2,000,000
Dividend per share, Depositary Shares																	$ 0.055382	$ 0.407812										$ 0.090625
Total Dividend, Depositary Shares																	221	816										181
Cost associated with share redemption	0	2,121	3,546	0	1,804	0	0	0	5,667	1,804	0								3,546	1,804									2,121
Preferred stock shares authorized	10,000,000								10,000,000
Partner's unit capital converted									105,028	535,026	125,784
Partner's Capital account exchange and conversions									996	4,763	1,109
Underwritten public offerings																						8,400,000	9,400,000	17,300,000
Net proceeds from underwriting																						132,050	116,715	201,150
Shares of common stock issuable under the at-the-market offering																																				12,500,000	10,000,000
Issuance of company common stock																																	2,315,704	1,532,598	115,856
Proceeds from common stock issuance ATM or DRIP																																	41,735	18,063	1,391
Aggregate gross sale proceeds																																				$ 125,000	$ 100,000