Supplementary Quarterly Financial Information (Unaudited) (Details Textuals) (USD $) In Millions, unless otherwise specified	3 Months Ended
Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Other Postretirement Benefit Expense Adjustment	$ 9
Other Postretirement Benefit Expense Adjustment, Net of Tax	$ 5

Other Postretirement Benefit Expense Adjustment, Net of Tax

No definition available.

Name:	deted_OtherPostretirementBenefitExpenseAdjustmentNetofTax
Namespace Prefix:	deted_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration