Summary of Significant Accounting Policies Supplemental Disclosures Related to Consolidated Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental cash flow information
Total interest costs incurred	$ 60,133	$ 58,074	$ 54,580
Interest capitalized	2,113	746	0
Interest expense	58,020	57,328	54,580
Cash paid for interest, net of amounts capitalized (including discontinued operations)	54,345	55,349	52,713
Cash paid for income taxes	901	1,239	172
Supplemental schedule of noncash investing and financing activities
Accounts payable and accrued liabilities for construction in progress	5,001	4,944	2,396
Accrued leasing commissions	1,385	(782)	0
Assumption of debt upon acquisition	0	0	268,008
Assumption of notes to affiliates upon acquisition	0	0	14,824
Acquisition of working capital deficit, net of cash	0	0	(4,176)
Distribution of investment in joint venture not acquired	0	0	11,480
Issuance of common shares and units for acquisition of properties	0	0	33,854
Notes receivable from affiliate settled in common units	0	0	21,797
Notes payable to affiliates settled in common units	0	0	828
Reduction to capital for prepaid equity financing costs	437	0	1,974
Transfer taxes accrued at time of initial public offering	$ 0	$ 0	$ 6,556