The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

Capital Stock and Derivative Instruments - Schedule of Vesting Shares Subject to Repurchase (Detail) - Restricted shares subject to repurchase [Member] - shares	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortization Expense [Line Items]
Unvested shares	3,761,496	4,039,591	4,197,396
1st quarter 2018 [Member]
Amortization Expense [Line Items]
Unvested shares	3,690,576
1st quarter 2019 [Member]
Amortization Expense [Line Items]
Unvested shares	70,920