Supplemental Disclosures Related to Consolidated Statements of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental cash flow information
Total interest costs incurred	$ 58,074	$ 54,580	$ 43,251
Interest capitalized	746
Interest expense	57,328	54,580	43,251
Cash paid for interest, net of amounts capitalized (including discontinued operations)	55,349	52,713	45,634
Cash paid for income taxes	1,239	172
Supplemental schedule of noncash investing and financing activities
Accounts payable and accrued liabilities for property under development	4,944	2,396	120
Assumption of debt upon acquisition (Note 2)		268,008	133,000
Assumption of notes to affiliates upon acquisition (Note 2)		14,824
Acquisition of working capital deficit, net of cash (Note 2)		(4,176)	(1,972)
Distribution of investment in joint venture not acquired		11,480
Issuance of common shares and units for acquisition of properties		33,854
Notes receivable from affiliate settled in common units		21,797
Notes payable to affiliates settled in common units		828
Reduction to capital for prepaid Offering costs		1,974
Transfer taxes accrued at time of Offering		$ 6,556