Schedule III - Carrying Cost and Accumulated Depreciation (Details) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Carrying cost:
Gross amount at beginning		$ 6,256,248	$ 6,093,541
Tenant capital improvements	$ 68,569	227,969	156,972
Acquisitions		80,132	15,848
Other		45,552
Total additions		353,653	172,820
Cost of real estate sold or disposed		6,421	10,113
Total deductions		6,421	10,113
Balance at end	6,093,541	6,603,480	6,256,248
Accumulated depreciation:
Gross amount of accumulated depreciation at beginning		4,054,748	3,720,890
Depreciation		351,332	343,971
Other		(45)
Total additions		351,287	343,971
Amount of accumulated depreciation for assets sold or disposed		6,246
Other			10,113
Total deductions		6,246	10,113
Balance at end	$ 3,720,890	$ 4,399,789	$ 4,054,748