Wexpro Agreement (Tables)

12 Months Ended

Dec. 31, 2012

Wexpro Agreement [Abstract]

Net investment base and yearly average rate of return

Wexpro's net investment base and the yearly average rate of return are shown in the table below:

	2012			2011			2010
Wexpro net investment base at December 31, (in millions)	$	531.1		$	474.4		$	456.6
Average annual rate of return (after tax)	19.9		%	20.0		%	20.0		%