8. Derivatives - Open crude oil derivative positions (Details) (USD $)	Dec. 31, 2014 bbl
Derivatives - Open Crude Oil Derivative Positions Details
Volume	1,500invest_InvestmentContractVolume
Fixed Swap Price	$ 90us-gaap_DerivativeSwapTypeFixedPrice

The volume of a commodity or material specified in an investment contract.

No definition available.

Name:	invest_InvestmentContractVolume
Namespace Prefix:	invest_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	instant