Supplementary Balance Sheet Information - Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Conversion costs
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, accumulated amortization	$ 161.6	$ 149.9
Payments for processing rights
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, accumulated amortization	$ 144.2	$ 137.9

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant