Summary of Company Information (Details)	Sep. 30, 2012 distribution_centers customer_locations
Summary of Company Information [Abstract]
Number of customer locations	29,000
Number of distribution centers	27
Number of distribution facilities operated as a third party logistics provider	2

Number of Distribution Facilities Operated as a Third Party Logistics Provider

No definition available.

Name:	core_NumberOfDistributionFacilitiesOperatedAsThirdPartyLogisticsProvider
Namespace Prefix:	core_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant