Financial Instruments and Concentrations of Risk (Details 2) - bbl bbl in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Sales [Member]
Derivative, Nonmonetary Notional Amount, Volume	23,228	6,773	2,595
Purchases [Member]
Derivative, Nonmonetary Notional Amount, Volume	22,946	6,477	2,575

Nominal volume used to calculate payments on a derivative instrument.

No definition available.

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration