Schedule III - Real Estate and Accumulated Depreciation Schedule III - Real Estate and Accumulated Depreciation (Summary) (Details) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
SEC Schedule III, Real Estate, Gross, January 1	$ 2,095,866,000	$ 1,988,849,000	$ 1,422,002,000
Payments to Acquire Property, Plant, and Equipment	394,737,000	124,113,000	533,171,000
Change In Accounts Payable, Real Property Additions	(430,000)	1,076,000	(995,000)
Additions Through Contingent Liabilities	0	(2,250,000)	3,000,000
Additions Through Assumption Of Debt	0	0	7,858,000
Payments for Delayed Tax Exempt Exchange	0	0	23,813,000
Conversion of mortgage note receivable to real estate	9,753,000	255,000	0
Additions Through Reclassification of Deposit	227,000	0	0
SEC Schedule III, Real Estate, Cost of Real Estate Sold	(27,299,000)	(13,563,000)	0
SEC Schedule III, Real Estate, Other Deductions	0	(2,614,000)	0
SEC Schedule III, Real Estate, Gross, December 31	2,472,854,000	2,095,866,000	1,988,849,000
SEC Schedule III, Real Estate Accumulated Depreciation, January 1	259,059,000	212,300,000	174,262,000
SEC Schedule III, Real Estate Accumulated Depreciation, Depreciation Expense	59,525,000	53,123,000	38,038,000
SEC Schedule III, Real Estate Accumulated Depreciation, Real Estate Sold	(5,504,000)	(5,096,000)	0
SEC Schedule III, Real Estate Accumulated Depreciation, Other Deductions	0	(1,268,000)	0
SEC Schedule III, Real Estate Accumulated Depreciation, December 31	$ 313,080,000	$ 259,059,000	$ 212,300,000