Income Taxes - Deferred Taxes - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Excess tax benefits (deficiency)	$ (0.8)	$ 8.4	$ 7.6

The tax effects of employee stock option transactions that are recognized differently for financial reporting and tax purposes, occurring during the period and charged or credited directly to shareholders' equity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 740

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6419406&loc=d3e23586-113945

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 740

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6419406&loc=d3e23594-113945

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 20

-Section 45

-Paragraph 11

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=18498875&loc=d3e39076-109324

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