Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 1997 Hardeman County Correctional Facilities Corporation
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		2,016
Outstanding principal balance of revenue bonds	28.8
Outstanding principal balance of the bonds exceeded the purchase price option	$ 8.4