Fair Value Measurements - Summary of Marketable Securities (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2016
U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities maturity period	1 year

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration