Changes in Outstanding Common Stock (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Capital Unit [Line Items]
Shares outstanding, beginning balance	83,193,310	82,156,400	61,944,706
Common stock issued through conversion of OP Units	29,566	749,814	656,706
Common stock issued through exercise of options	20,000	160,000	344,768
Common stock issued through stock grants	173,333	177,998	216,664
Common stock issued through ESPP and Dividend Reinvestment Plan	19,012	31,108	30,304
Common stock repurchased and retired	(121,544)	(82,010)	(8,300)
Common stock issued through stock offering	0	0	12,075,000
Shares outstanding, ending balance	83,313,677	83,193,310	82,156,400
Common Stock
Capital Unit [Line Items]
Stock issued for acquisition properties	0	0	3,416,552
Series B Subordinated Non-Voting Cumulative Redeemable Preferred Stock
Capital Unit [Line Items]
Stock issued for acquisition properties	0	0	3,480,000