Investments (Summary Financial Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Investments [Abstract]
Operating revenues	$ 150.3	$ 142.8	$ 450.1	$ 420.6
Operating income	81.5	76.4	240.0	228.1
Net income	$ 60.5	$ 56.6	$ 177.9	$ 166.5

The amount of gross profit (loss) reported by an equity method investment of the entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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

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+ Details

- Definition

The amount of net income (loss) reported by an equity method investment of the entity.

+ References

+ Details