Real Estate Transactions - Additional Information (Detail) $ in Thousands, MMcf in Millions												1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 21, 2018 USD ($) ft² Option MMcf	Aug. 23, 2018 USD ($) ft²	Jul. 17, 2018 USD ($) Property	Jan. 24, 2018 Bed	Jan. 19, 2018 USD ($) ft²	Jan. 19, 2018 USD ($) ft²	Sep. 15, 2017 USD ($) Bed Property	Aug. 01, 2017 USD ($) Bed	Feb. 10, 2017 USD ($) Bed	Jan. 02, 2017 USD ($)	Jun. 10, 2016 USD ($) Bed	May 31, 2016 USD ($) Bed	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) Facility Bed Property	Dec. 31, 2017 USD ($) Acquisition	Dec. 31, 2016 USD ($)	Jan. 01, 2017 Bed
Facility Activations Developments And Closures [Line Items]
Number of beds at the facility | Bed											112
Lease expiration date											2020-06
Lease extension period											5 years
Purchase price of real estate			$ 12,000				$ 8,700				$ 7,700
Percentage of building leased			100.00%
Purchase price, net tangible assets			$ 11,100								7,400				$ 20,100
Purchase price, identifiable intangible assets			$ 1,900								$ 300				$ 1,800
Number of properties acquired | Property			12				4							15
Number of acquisitions | Acquisition															4
Number of properties that may be marketed under portfolio acquisition			up to three
Business acquisition assumed in-place financing														$ 157,280
Operating Expense														1,315,250	$ 1,249,537	$ 1,275,586
Proceeds from sale of corporate headquarters													$ 12,600
Asset impairments													$ 1,600	$ 1,580	614
Idle Facilities
Facility Activations Developments And Closures [Line Items]
Number of facility | Facility														8
Operating Expense														$ 12,400	10,800	$ 8,100
Idled Non-Core Facilities
Facility Activations Developments And Closures [Line Items]
Number of beds at the facility | Bed														440
Number of facility | Facility														2
Net Carrying Value														$ 3,800
Oklahoma Department Of Corrections
Facility Activations Developments And Closures [Line Items]
Number of beds at the facility | Bed												2,400
Operating leases agreement renewal term												2 years
Lease agreement commencing date												Jul. 01, 2016
Lease term												5 years
Average annual rent												$ 7,300
Annual rent year five												$ 12,000
Kansas Department Of Corrections
Facility Activations Developments And Closures [Line Items]
Number of beds at the facility | Bed				2,432
Lease term				20 years
Construction of new facility commencement description														Construction of the new facility commenced in the first quarter of 2018 with a timeline for completion of approximately 24 months.
Construction of new facility approximate completion term				24 months
Construction project capitalized amount														$ 58,600
North Carolina and Georgia | Internal Revenue Service ("IRS")
Facility Activations Developments And Closures [Line Items]
Number of properties leased | Property							1
North Carolina and Georgia | General Services Administration
Facility Activations Developments And Closures [Line Items]
Number of properties leased | Property							3
North Carolina and Georgia | Social Security Administration
Facility Activations Developments And Closures [Line Items]
Number of properties leased | Property							2
North Carolina
Facility Activations Developments And Closures [Line Items]
Purchase price, tenant improvements															$ 300
Residential Reentry Centers
Facility Activations Developments And Closures [Line Items]
Number of beds at the center | Bed							230
Arapahoe Community Treatment Center
Facility Activations Developments And Closures [Line Items]
Purchase price of real estate										$ 5,500
Number of beds at the center | Bed																	135
Stockton Female Community Corrections Facility
Facility Activations Developments And Closures [Line Items]
Lease expiration date									2021-04
Lease extension period									5 years
Purchase price of real estate									$ 1,600
Number of beds at the center | Bed									100
New Beginnings Treatment Center, Inc.
Facility Activations Developments And Closures [Line Items]
Purchase price of real estate								$ 6,400
Number of beds at the center | Bed								92
Capital Commerce Center
Facility Activations Developments And Closures [Line Items]
Area of building acquired | ft²					261,000	261,000
Purchase price of real estate					$ 44,700	$ 44,700
Percentage of building leased						98.00%
Purchase price, net tangible assets						$ 40,600
Purchase price, identifiable intangible assets						$ 3,200
Capital Commerce Center | Florida
Facility Activations Developments And Closures [Line Items]
Percentage of building leased						87.00%
Social Security Administration
Facility Activations Developments And Closures [Line Items]
Area of building acquired | ft²		541,000
Purchase price of real estate		$ 242,000
Purchase price, net tangible assets		207,400
Purchase price, identifiable intangible assets		$ 38,900
Lease term		20 years
Lease term expiration date		Jan. 31, 2034
Business acquisition assumed in-place financing		$ 157,300
National Archives And Records Administration
Facility Activations Developments And Closures [Line Items]
Area of building acquired | ft²	217,000
Purchase price of real estate	$ 6,900
Percentage of building leased	100.00%
Purchase price, net tangible assets	$ 6,900
Purchase price, identifiable intangible assets	$ 700
Lease term expiration date	Jan. 31, 2023
Additional ten year renewal options | Option	2
Renewal of contract terms	10 years
Volume of storage space | MMcf	1.2
Percentage of storage space	90.00%