Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Y D Bed	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 After Two Years Of Service	Dec. 31, 2012 After Three Years Of Service	Dec. 31, 2012 After Four Years Of Service	Dec. 31, 2012 After Five Or More Years Of Service	Dec. 31, 2012 Executive Officer	Dec. 31, 2012 Non Employee Directors	Dec. 31, 2012 Hardeman County Correctional Facilities Corporation	Dec. 31, 1997 Hardeman County Correctional Facilities Corporation Facility
Loss Contingencies [Line Items]
Number of pending legal proceedings that would have an effect on consolidated financial position, results of operations, or cash flows	0
Issuance of revenue bonds											$ 72.7
Number of beds at the facility	92,500										2,016
Outstanding principal balance of revenue bonds										28.8
Outstanding principal balance of the bonds exceeded the purchase price option										9.3
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 hours
Vested percentage of employer contributions and investment earnings or losses				20.00%	40.00%	80.00%	100.00%
Discretionary contribution plan forfeitures, net	11.1	9.2	8.3
Number of qualified deferred compensation plans	2
Contribution as percentage of salary								50.00%
Contribution as percentage of cash bonus								100.00%
Contribution as percentage of retainer and meeting fees									100.00%
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 form Deferred Compensation Plans to participants	5.90%	6.00%	6.20%
Deferred Compensation Plans assets	12.6	8.8
Matching contributions as general and administrative expense associated with the Deferred Compensation Plans	0.5	0.3	0.3
Deferred Compensation Plans liability	$ 15.6	$ 12.2