Share Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended
	Feb. 17, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Performance Unit Plan [Abstract]
Performance units granted	16,693
Accelerated compensation costs from amendment		$ 0.5
Compensation expense			0.8	0.8
Cash payments for prior activity			0.6
Forfeitures			0	0
Vested awards			$ 2.8