Investments in Marketable Securities - Cost, Gross Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Marketable Securities [Abstract]
Cost	$ 61.6	$ 57.9
Unrealized gains	0.4	2.1
Unrealized losses	(7.4)	(0.6)
Fair value	$ 54.6	$ 59.4

Amount of investment in marketable security.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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

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