Equity Income from Unconsolidated Subsidiaries (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Summarized financial information for unconsolidated subsidiary, LTM
Contract revenue earned	$ 2.5	$ 3.8	$ 10.5	$ 10.2
Gross profit	0.8	1.4	5.2	2.0
Net income	1.1	1.4	5.5	2.0
Current assets	6.9		6.9		7.3
Current liabilities	$ 6.5		$ 6.5		$ 9.8