Investment in ProLiance Holdings, LLC (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
ProLiance Holdings, LLC [Abstract]
Equity method investment, profit and loss ownership percentage (in hundredths)	61.00%
Equity method investment, ownership percentage (in hundredths)	50.00%
Summarized balance sheet information:
Current assets	$ 381.9	$ 441.4
Noncurrent assets	56.1	59.1
Current liabilities	298.5	298.1
Noncurrent liabilities	0.7	0.4
Members' equity	161.5	208.9
Accumulated other comprehensive income (loss)	(26.0)	(10.8)
Noncontrolling interest	3.3	3.9
Investments in unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	92.9	135.2
Equity in earnings (losses) of unconsolidated affiliates	(32.0)	(8.6)	3.4
Equity method investment holding minority interest in equity method investment (in hundredths)	25.00%
Equity method investment minority interest in joint ventures	35.1	36.7
Impairment Charge Recorded By Investee Of Companys Equity Method Investments			132.0
Equity method investment unusual item gain or loss net of tax attributable to noncontrolling interest			11.9
Reduction to Equity in earnings of unconsolidated affiliates-gross			19.9
Income tax benefit due to gain or loss			8.0
Loss contingency, gross damages sought from a party that entered into a sub-lease agreement with a party that is an investment of an equity method investee.	56.7
Firm transportation and storage agreements due within one year of the balance sheet date	55.5
Firm transportation and storage agreements due in more than one and within two years of the balance sheet date	49.0
Firm transportation and storage agreements due in more than two and within three years of the balance sheet date	46.6
Firm transportation and storage agreements due in more than three and within four years of the balance sheet date	38.2
Firm transportation and storage agreements due in more than four and within five years of the balance sheet date	33.9
Firm transportation and storage agreements due after five years from the balance sheet date	247.9
Fixed payments for firm storage and transportation commitments	73.0	76.8	63.0
Purchases from ProLiance for resale and for injections into storage	378.7	437.7	533.4
Amounts owed to ProLiance for those purchases	36.8	59.6
ProLiance Holdings, LLC [Member]
Investments in unconsolidated Affiliates [Line Items]
Investments in unconsolidated affiliates	85.4	123.2
Equity in earnings (losses) of unconsolidated affiliates	(28.6)	(2.5)	3.6
Summarized Statement of Income [Member]
Summarized Statement of Income information [Abstract]
Revenues	1,410.5	1,497.0	1,654.9
Operating income (loss)	(44.5)	(3.1)	35.2
Charge related to Investment in Liberty Gas Storage	0	0	(32.7)
ProLiance's earnings (losses)	$ (47.3)	$ (3.7)	$ 4.5