Long-Term Obligations (Details) (Equipment Financing Arrangement, USD $) In Millions, unless otherwise specified	1 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 Y	Dec. 31, 2011
Long-term obligations
Draw down period (in years)		3
Basis for variable interest rate		three-year interest rate swap
Additional principal amount drawn during the period	$ 9.1
Principal drawn down under loan agreement	27.4	27.4
Interest rate on new draw down (as a percent)	4.12%	4.12%
Weighted average interest rate (as a percent)	5.51%	5.51%
Maximum borrowing capacity for equipment purchases	6.0	6.0
Total	$ 12.6	$ 12.6	$ 5.3
Minimum
Long-term obligations
Percentage added to variable rate basis	3.50%	3.50%
Maximum
Long-term obligations
Percentage added to variable rate basis	4.00%	4.00%