Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified		1 Months Ended	3 Months Ended
	Dec. 31, 2012	Aug. 31, 2011 Class Action Settlement Agreement and Fund	Jun. 30, 2011 Class Action Settlement Agreement and Fund	Dec. 31, 2009 Class Action Settlement Agreement and Fund	Dec. 31, 2012 Letters of credit
Contingencies
Letters of credit amount issued	$ 9.9				$ 9.5
Accrued litigation contingencies				7.0
Amount paid by Shoppers pursuant to settlement agreement			7.0
Unclaimed settlement funds reverted back to Shoppers		$ 1.3