Debt - Summary of Scheduled Debt Maturities, Including Balloon Payments (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2017
Debt Instrument [Line Items]
Revolving facility optional extension period	1 year
Revolving Facility [Member]
Debt Instrument [Line Items]
Credit facility agreement, maturity date	Jun. 02, 2018
Revolving facility optional extension period	1 year

Date the credit facility terminates, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration