Summary of Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Supplemental cash flow information
Total interest costs incurred			$ 43,983	$ 41,791
Interest capitalized			461
Interest expense	14,690	14,738	43,522	41,791
Cash paid for interest, net of amounts capitalized			40,527	39,158
Cash paid for income taxes			1,210	55
Supplemental schedule of noncash investing and financing activities
Accounts payable and accrued liabilities for construction in progress			5,635	1,525
Assumption of debt upon acquisition				268,008
Assumption of notes to affiliates upon acquisition				14,824
Acquisition of working capital deficit, net of cash				(4,175)
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