Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial Assets:
Interest rate swap agreements	$ 474	$ 1,131
Carrying Amount
Financial Assets:
Cash and cash equivalents	74,961	116,241
Mortgage loan receivable	3,331	3,417
Interest rate swap agreements	474	1,131
Financial Liabilities:
Mortgage notes payable	1,238,336	1,339,450
Notes payable to banks	550,000	481,500
Interest rate swap agreements	9,026	11,077
Fair Value
Financial Assets:
Cash and cash equivalents	74,961	116,241
Mortgage loan receivable	3,331	3,417
Interest rate swap agreements	474	1,131
Financial Liabilities:
Mortgage notes payable	1,235,553	1,327,637
Notes payable to banks	548,414	477,967
Interest rate swap agreements	$ 9,026	$ 11,077