Consolidated Statements of Comprehensive Income (Parenthetical) (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Reclassifications of prior service benefit and actuarial loss, tax benefit	$ 0.2	$ 0.3	$ 0.9	$ 0.9

Tax effect of the income statement impact of the reclassification adjustment for the net transition asset (obligation) recognized as a component of net periodic benefit cost.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e640-108580

Name:	us-gaap_OtherComprehensiveIncomeLossReclassificationPensionAndOtherPostretirementBenefitPlansNetTransitionAssetObligationRecognizedInNetPeriodicBenefitCostTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration