Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Income Taxes - Tax Act (Details) - USD ($) $ in Millions	3 Months Ended	8 Months Ended	9 Months Ended	12 Months Ended		16 Months Ended
Income Taxes - Tax Act (Details) - USD ($) $ in Millions	Jan. 31, 2018	Dec. 31, 2017	Jan. 31, 2018	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2019
Income Taxes
Federal statutory rate (as a percent)		35.00%				21.00%
Provisional income tax benefit	$ 7.8				$ 6.7
Decrease from provisional amount	$ 1.1		$ 1.1
Income tax benefit related to tax adjustments made				$ 0.1