Equity and Noncontrolling Interests - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011 7-5/8% Series B Cumulative Redeemable Shares [Member]	Dec. 31, 2012 At-The-Market Common Equity Sales Program [Member]	Dec. 31, 2011 At-The-Market Common Equity Sales Program [Member]	Dec. 31, 2010 At-The-Market Common Equity Sales Program [Member]	May 31, 2012 At-The-Market Common Equity Sales Program [Member]	Dec. 31, 2012 At-The-Market Common Equity Sales Program [Member] Gross [Member]	Dec. 31, 2011 At-The-Market Common Equity Sales Program [Member] Gross [Member]	Dec. 31, 2010 At-The-Market Common Equity Sales Program [Member] Gross [Member]	Dec. 31, 2012 At-The-Market Common Equity Sales Program [Member] Net [Member]	Dec. 31, 2011 At-The-Market Common Equity Sales Program [Member] Net [Member]	Dec. 31, 2010 At-The-Market Common Equity Sales Program [Member] Net [Member]
Equity And Noncontrolling Interests [Line Items]
Common stock, shares authorized	100,000	100,000						4,000
Common stock, shares issued					4,000
Sale of common stock, shares					550	3,409	41
Proceeds from sales of common stock	$ 25,457	$ 135,651	$ 1,121						$ 26,153	$ 138,628	$ 1,144	$ 25,457	$ 135,651	$ 1,121
Sales price per share					$ 47.55	$ 40.67	$ 27.70
Stock repurchase program, authorized amount	200,000
Shares of common stock repurchased	0	0	0
Redemption of preferred stock		49,633	2,021	49,571
Preferred stock redemption amount exceeds carrying value				1,757
Carrying value reduction of earnings common unitholders				1,757
Repurchase of preferred stock			2,037
Redeemable common units	7,159	6,840
Noncontrolling interests in the Operating Partnership, net book value	$ 2,820	$ 2,935