Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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

Financial Instruments - Schedule of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Interest rate cap, fair value	$ 22.2		$ 5.4
Cap agreement effective 1/17/17-12/31/18
Derivative [Line Items]
Notional amount	1,400.0
Interest rate cap, fair value	3.2		5.4
Cap agreement effective 12/31/18-12/31/20
Derivative [Line Items]
Notional amount	1,400.0	$ 1,400.0
Interest rate cap, fair value	$ 19.0		$ 0.0