Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets
Trading securities	$ 0.3	$ 2.5
Liabilities
Contingent consideration associated with CDI acquisition		0.3
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Trading securities	0.3	2.5
Liabilities
Contingent consideration associated with CDI acquisition		0.0
Significant Other Observable Inputs (Level 2)
Assets
Trading securities
Liabilities
Contingent consideration associated with CDI acquisition		0.0
Unobservable Inputs (Level 3)
Assets
Trading securities	$ 0.0	0.0
Liabilities
Contingent consideration associated with CDI acquisition		$ 0.3

Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26626-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

Name:	us-gaap_TradingSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant