Operating Segments, Geographic Analysis and Major Customers (Details 3) (Total operating revenues, Operating revenues, BP)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Total operating revenues \| Operating revenues \| BP
Concentration Risk
Percentage of concentration	10.00%	10.00%	12.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

No definition available.

Name:	us-gaap_ConcentrationRiskPercentage
Namespace Prefix:	us-gaap_
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant