Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2012

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum rental payments for operating leases

(in millions)	Total		2013		2014		2015		2016		2017		Thereafter
Operating leases(1)	$	18.0	$	5.1	$	5.3	$	3.6	$	2.9	$	1.1	$	—
Drilling rig commitments(2)	9.4		9.4		—		—		—		—		—
Other commitments(3)	23.5		16.2		2.9		2.3		2.1		—		—
Firm natural gas transportation contracts(4)	245.1		31.0		33.7		33.4		33.5		33.4		80.1
Total	$	296.0	$	61.7	$	41.9	$	39.3	$	38.5	$	34.5	$	80.1

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(1) Includes operating leases related to office facilities, vehicles, rail cars and aircraft.

(2) Excludes obligations related to rigs drilling on a well-by-well basis that can be released after drilling the current well without penalty.

(3) Includes primarily obligations related to natural gas purchases, cogeneration facility management services, California carbon allowance forward purchase contracts and equipment rentals.

(4) The Company enters into certain firm commitments to transport natural gas production to market and to transport natural gas for use in its cogeneration and conventional steam generation facilities. These commitments generally require a minimum monthly charge regardless of whether the contracted capacity is used or not.