Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Feb. 28, 2014	Dec. 31, 2014 Y LegalMatter D Bed	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 1997 Facility
Loss Contingencies [Line Items]
Compensation amount on contractual disputes	$ (1)
Number of pending legal proceedings that would have an effect on consolidated financial position, results of operations, or cash flows		0
Number of beds at the facility		84,500
Minimum age limit for participating in the Savings and Retirement Plan, years		18
Minimum qualified service required to participate in the Savings and Retirement Plan, years		1
Eligible employee contribution on eligible compensation		90.00%
Employer discretionary matching contribution equal to employee contribution		100.00%	100.00%	100.00%
Maximum percentage of employer discretionary matching contribution of employee eligible compensation		5.00%	5.00%	5.00%
Minimum number of hours of employment in the plan year for discretionary matching contribution		One thousand
Discretionary contribution plan forfeitures, net		11.1	11.8	11.1
Number of qualified deferred compensation plans		2
Total cash compensation under Deferred Compensation Plans		5.00%	5.00%	5.00%
Time period when distributions are paid, minimum years subsequent to the date an individual becomes a participant in the Plan		5
Distributions to senior executives commencement period, days after participant's separation from service		60
Distributions to senior executives commencement period, time period		The fifteenth day of the month following the month the individual attains age 65.
Percentage of fixed return from Deferred Compensation Plans to participants		5.60%	5.60%	5.90%
Deferred Compensation Plans assets		17.9	15.8
Matching contributions as general and administrative expense associated with the Deferred Compensation Plans		0.2	0.2	0.5
Deferred Compensation Plans liability		15.7	16.4
Executive Officer
Loss Contingencies [Line Items]
Contribution as percentage of salary		50.00%
Contribution as percentage of cash bonus		100.00%
Non Employee Directors
Loss Contingencies [Line Items]
Contribution as percentage of retainer and meeting fees		100.00%
Prior to January One Twenty Twelve | After Two Years Of Service
Loss Contingencies [Line Items]
Vested percentage of employer contributions and investment earnings or losses		20.00%
Prior to January One Twenty Twelve | After Three Years Of Service
Loss Contingencies [Line Items]
Vested percentage of employer contributions and investment earnings or losses		40.00%
Prior to January One Twenty Twelve | After Four Years Of Service
Loss Contingencies [Line Items]
Vested percentage of employer contributions and investment earnings or losses		80.00%
Prior to January One Twenty Twelve | After Five Or More Years Of Service
Loss Contingencies [Line Items]
Vested percentage of employer contributions and investment earnings or losses		100.00%
Hardeman County Correctional Facilities Corporation
Loss Contingencies [Line Items]
Issuance of revenue bonds					72.7
Number of beds at the facility					2,016
Outstanding principal balance of revenue bonds		18.6
Outstanding principal balance of the bonds exceeded the purchase price option		$ 7.3