Business Combinations - Contingent Consideration Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2021
Contingent Consideration
Balance at December 31, 2020		$ 20.1
Increase in fair value of contingent consideration liabilities		2.0
Balance at June 30, 2021	$ 22.1	22.1
SES
Contingent Consideration
Balance at December 31, 2020		16.9
Increase in fair value of contingent consideration liabilities	1.3	2.0
Balance at June 30, 2021	18.9	18.9
BIG
Contingent Consideration
Balance at December 31, 2020		3.2
Increase in fair value of contingent consideration liabilities	(0.1)	0.0
Balance at June 30, 2021	$ 3.2	$ 3.2

Amount of liability recognized arising from contingent consideration in a business combination.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

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