Financial and Other Derivative Instruments (Details Textuals) (FTR [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
FTR [Member]
Derivative [Line Items]
Derivative Instruments Recoverable Through PSCR Mechanism	$ 1	$ 1

Derivative Instruments Recoverable Through PSCR Mechanism

No definition available.

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