Derivative Instruments (Details Textual)	3 Months Ended
Mar. 31, 2013	Apr. 30, 2013
Derivative Instruments (Additional Textual) [Abstract]
Hedging up projected proved for twelve months, rate	90.00%
Hedging up projected proved for twenty four months rate	80.00%
Number of additional derivative contracts	1	1

Percentage of proved reserves allowed to be hedged under credit facility for the ensuring 24 months.

No definition available.

Name:	dble_HedgingUpProjectedProvedForTwentyFourMonthsRate
Namespace Prefix:	dble_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration