Consolidated Statement of Comprehensive Income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Income and Comprehensive Income [Abstract]
Tax benefit (provision) on unrealized gains and losses on available-for-sale investments included in other comprehensive income	$ (1.1)	$ (0.5)	$ (0.9)
Tax benefit (provision) on unrealized gains and losses on hedging instruments included in other comprehensive income	21.7	(0.1)	(0.1)
Tax benefit (provision) on pension and other postretirement benefit liability adjustments in other comprehensive income	$ 36.9	$ 9.7	$ (20.9)

Tax effect of the gross appreciation or the gross loss, net of reclassification adjustment, in the value of the total unsold available-for-sale securities at the end of an accounting period.

+ References+ Details

Tax effects of the increase (decrease) to accumulated comprehensive income during the period related to benefit plans. While for technical reasons this element has no balance attribute, the default assumption is a credit balance consistent with its label.

+ References+ Details

- Definition

Total tax effect of the change in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. The change includes an entity's share of an equity investee's increase or decrease in deferred hedging gains or losses. While for technical reasons this element has no balance attribute, the default assumption is a credit balance consistent with its label.

+ References+ Details