Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Investments other-than-temporarily impaired	$ 0	$ 0
Investments maturity period	2 years	2 years
Realized losses	$ 0
Other-than-temporary impairments of available-for-sale securities	$ 0

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27161-111563

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsAvailableforsaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration