Debt - Senior Notes (Details) - Senior Notes [Member] - USD ($)	Mar. 31, 2020	Mar. 31, 2019
Senior Notes, Due 2023
Debt Instrument [Line Items]
Debt face amount		$ 300,000,000.0
Average interest rate	3.95%	3.95%
Senior Notes, Due 2028
Debt Instrument [Line Items]
Debt face amount		$ 500,000,000.0
Average interest rate	4.55%	4.55%

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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