Short-Term Debt - Additional Information (Detail)	3 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Line Of Credit Facility [Line Items]
Weighted-average interest rate	3.31%	3.14%
Minimum [Member]
Line Of Credit Facility [Line Items]
Commitment fees, percentage	0.125%
Maximum [Member]
Line Of Credit Facility [Line Items]
Commitment fees, percentage	0.35%

Weighted average interest rate of short-term debt outstanding calculated at point in time.

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

Name:	us-gaap_ShortTermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant