Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Disclosure of Cash Flow Information:
Interest paid	$ 52,688	$ 42,666	$ 41,460
Income taxes paid	996	889	669
Investing Activities:
Accrued capital expenditures	5,696	3,853	1,783
Note receivable included in the consideration of an acquisition	0	11,924	0
Debt and interest rate swaps assumed in acquisitions	0	103,980	55,977
Financing Activities:
Dividend distributions declared, but not paid	37,886	36,275	34,177
Issuance of operating partnership units in connection with acquisitions	$ 0	$ 16,960	$ 0