Stockholders' Equity (Components of Comprehensive Income, Net of Tax) (Details) (USD $) In Millions	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stockholders' Equity
Net income	$ 117.4	$ 88.7	$ 221.5	$ 174.0
Foreign currency translation gains (losses)	0	(0.4)	0.3	(0.6)
Unrealized gains (losses) on derivative instruments	(0.1)	1.1	(1.7)	3.1
Reclassification adjustment for (gains) losses on derivative instruments recognized during the period	1.0	(2.2)	1.6	(3.1)
Unrealized gains on available-for-sale securities, net of tax	2.4	0	0.8	0
Total other comprehensive income	$ 120.7	$ 87.2	$ 222.5	$ 173.4

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the economic entity, including both controlling (parent) and noncontrolling interests. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, including any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

+ References+ Details

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

- Definition

Change in the balance sheet adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into functional currency of the reporting entity for the period being reported, net of tax. If an entity's functional currency is a foreign currency, translation adjustments result from the process of translating that entity's financial statements into the reporting currency. Includes gain (loss) on foreign currency forward exchange contracts. Includes foreign currency transactions designated as hedges of net investment in a foreign entity and intercompany foreign currency transactions that are of a long-term nature, when the entities to the transaction are consolidated, combined, or accounted for by the equity method in the reporting enterprise's financial statements. Includes the gain (loss) on a derivative instrument or nonderivative financial instrument that may give rise to a foreign currency transaction gain (loss) and that have been designated and have qualified as hedging instruments for hedges of the foreign currency exposure of a net investment in a foreign operation.

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+ Details

- Definition

Net of tax effect of the reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period.

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+ Details

- Definition

Change in accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges, net of tax effect. The after tax effect change includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

+ References

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+ Details

- Definition

Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain (loss), net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain (loss) at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains (losses) realized upon the sale of securities, after tax; and (3) the unrealized gains (losses) realized upon the write-down of securities, after tax.

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+ Details