Stockholders' Equity - Market-Based Restricted Stock Units - Additional Information (Detail) - Market-based RSUs [Member] - shares	6 Months Ended	12 Months Ended
Dec. 31, 2017	Jun. 30, 2017
Class of Stock [Line Items]
Restricted stock units issued	700,000	700,000
2008 Incentive Plan [Member]
Class of Stock [Line Items]
Restricted stock units issued	200,000	200,000
President and CEO [Member]
Class of Stock [Line Items]
Restricted stock units issued	500,000	500,000

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration