Stockholders' Equity - Fair Value of Employee Stock Options (Parenthetical) (Detail)	3 Months Ended
Jun. 30, 2019 USD ($)
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options granted	$ 0

Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration