Supplemental Disclosures of Cash Flow Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Supplemental Disclosures of Cash Flow Information
Cash paid for interest	$ 105,600,000	$ 114,600,000
Interest capitalized to properties under development	212,000	266,000
Cash paid for income taxes	3,400,000	3,100,000
Non-cash investing and financing activities
Loans Assumed	32,500,000	$ 0
Net premiums recorded on mortgages assumed	$ 692,000