INVENTORIES Inventory Disclosure (Details) (PGL [Member], USD $)	Sep. 30, 2013
PGL [Member]
Temporary LIFO liquidation credit [Line Items]
Temporary LIFO Liquidation Credit	$ 0

Represents the difference between current projected replacement cost and the LIFO cost for quantities of natural gas temporarily withdrawn from storage.

No definition available.

Name:	teg_TemporaryLIFOLiquidationCredit
Namespace Prefix:	teg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant