Fair Value Measurements, Available-for-sale Securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Market Value	$ 39.9	$ 36.6
Cost Basis	30.0	31.4
Gross Unrealized Gains	10.4	5.9
Gross Unrealized Losses	0.5	0.7
Trading Securities		4.3
Mutual Fund and Unit Trust Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	35.6	32.0
Cost Basis	25.2	26.1
Gross Unrealized Gains	10.4	5.9
Gross Unrealized Losses	0	0
Auction Rate Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Market Value	4.3	4.6
Cost Basis	4.8	5.3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	$ 0.5	$ 0.7

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details

- Definition

Financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time, usually less than one year or the normal operating cycle, whichever is longer) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

+ References

+ Details