Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental Disclosure of Cash Flow Information:
Interest paid	$ 41,460	$ 38,560	$ 38,288
Income taxes paid	669	1,090	1,045
Investing Activities:
Accrued capital expenditures	1,783	1,575	5,448
Note receivable included in the consideration for the acquisition of a building	0	37,264	0
The following represents the significant increase (decrease) in certain assets and liabilities in connection with our acquisition of operating properties:
Debt and interest rate swaps	55,977	0	6,657
Financing Activities:
Issuances under the DRIP	0	31,916	75,864
Dividend distributions declared, but not paid, including under the DRIP	34,177	30,959	14,120
Offering costs transferred to equity/partners’ capital	$ 1,323	$ 0	$ 0