Schedule III: Rollforward of Real Estate Assets and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Real Estate and Accumulated Depreciation [Line Items]
Balance at beginning of period	$ 993,927	$ 919,576	$ 911,792
Subtotal real estate	1,040,662	993,984	919,576
Less: Fully depreciated assets	(11,190)	(57)	0
Balance at end of the period	1,029,472	993,927	919,576
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at beginning of period	210,025	185,375	160,826
Additions charged to operating expenses	26,698	24,707	24,549
Subtotal of accumulated depreciation	236,723	210,082	185,375
Less: Fully depreciated assets	(11,190)	(57)	0
Balance at end of the period	225,533	210,025	185,375
Land [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate, Improvements	0	0	0
Buildings and leasehold improvements [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate, Improvements	112,538	4,043	5,072
Development and construction in progress [Member]
Real Estate and Accumulated Depreciation [Line Items]
Real Estate, Improvements	$ (65,803)	$ 70,365	$ 2,712