Schedule III - Real Estate Assets and Accumulated Depreciation Summary of Transactions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
SEC Schedule III, Real Estate Assets and Accumulated Depreciation [Line Items]
Investment in Real Estate, balance at beginning of period	$ 3,367,358		$ 3,306,896	$ 3,246,119
Additions through capital expenditures	26,547		29,730	20,498
Acquisitions	269,271		37,827	36,199
Asset Impairments			(879)
Reclassifications and other	33,984		(6,216)	4,080
Investment in Real Estate, balance at end of period	3,697,160	[1]	3,367,358	3,306,896
Accumulated Depreciation, balance at beginning of period	(976,121)		(888,745)	(772,112)
Depreciation	(99,361)		(94,116)	(116,726)
Disposals/Other	93		6,162	93
Asset Impairments			578
Accumulated Depreciation, balance at end of period	$ (1,075,389)	[2]	$ (976,121)	$ (888,745)

[1] The aggregate cost of properties for federal income tax purposes is approximately $3.9 billion at December 31, 2018.

[2] Depreciation is calculated using estimated useful lives of depreciable assets up to 50 years for prison facilities.