The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Employee Benefit Plans - Equity Incentive Plan (Details) - shares shares in Millions	Apr. 01, 2019	Sep. 30, 2019
Share-Based Compensation Plans
Stock options, RSUs, and RSAs assumed in acquisition (in shares)	1.9
Equity incentive plan 2015
Share-Based Compensation Plans
Number of shares available for future issuance (in shares)		16.2
Employee stock purchase plan 2008
Share-Based Compensation Plans
Number of shares available for future issuance (in shares)		6.3