LIFO Inventory Decrement

No definition available.

Name:	core_LIFOInventoryDecrement
Namespace Prefix:	core_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of FIFO (first in first out) inventory present at the reporting date when inventory is also valued using different valuation methods.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766

+ Details

Name:	us-gaap_FIFOInventoryAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of difference between inventory at lower of LIFO cost or market and inventory at lower of other inventory accounting method cost or market, for example, but not limited to, FIFO or average cost.

+ References

+ Details

Name:	us-gaap_InventoryLIFOReserve
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The difference between the change in the inventory reserve representing the cumulative difference in cost between the first in, first out and the last in, first out inventory valuation methods and any LIFO decrement which have been reflected in the statement of income during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_InventoryLIFOReserveEffectOnIncomeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_InventoryLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 330

-SubTopic 10

-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6386567&loc=d3e3927-108312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

+ Details

Name:	us-gaap_InventoryNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Inventories (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Inventory [Line Items]
Inventories at FIFO, net of reserves	$ 533.1us-gaap_FIFOInventoryAmount				$ 488.2us-gaap_FIFOInventoryAmount				$ 533.1us-gaap_FIFOInventoryAmount	$ 488.2us-gaap_FIFOInventoryAmount
Less: LIFO reserve	(115.3)us-gaap_InventoryLIFOReserve				(99.0)us-gaap_InventoryLIFOReserve				(115.3)us-gaap_InventoryLIFOReserve	(99.0)us-gaap_InventoryLIFOReserve
Total inventories at LIFO, net of reserves	417.8us-gaap_InventoryNet				389.2us-gaap_InventoryNet				417.8us-gaap_InventoryNet	389.2us-gaap_InventoryNet
LIFO expense	2.7	6.5	4.3	2.8	(0.1)	2.2	3.7	2.9	16.3	8.7	12.3
LIFO decrement									4.6core_LIFOInventoryDecrement	11.8core_LIFOInventoryDecrement
United States [Member]
Inventory [Line Items]
Less: LIFO reserve	$ (115.3)				$ (99.0)				$ (115.3)	$ (99.0)