Supplemental Cash Flow Information (Schedule of Supplemental Cash Flow Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Non-cash investing and financing activities:
Interest paid, net of amounts capitalized	$ 6,588	$ 5,402	$ 7,188
Income taxes paid, net of refunds	125	140	135
Property and equipment additions and purchases of real estate in accrued liabilities	749	2,580	1,479
Capital expenditures for real estate under development in accounts payable and accrued liabilities	0	1,940	1,817
Transfer from real estate under development to building and improvements	0	108	3,346
Additions to building and building improvements reclassified from real estate under development	37,110	6,879	0
Additions to land and land improvements reclassified from real estate under development	3,685	542	170
Additions to furniture, fixtures, and equipment reclassified from real estate under development	1,101	0	211
Amortization of deferred financing fees in properties under development	10	88	31
Transfer of noncontrolling interest	0	0	2,136
Capitalized deferred financing costs in accrued liabilities	0	0	31
Deed in lieu of foreclosure:
Real estate and lease intangibles	12,723	0	0
Note payable	15,853	0	0
Northborough Tower
Deed in lieu of foreclosure:
Other assets and liabilities, net	$ 1,506	$ 0	$ 0