Carrying value of amounts transferred to third parties for security purposes that are expected to be returned or applied towards payment in the future.

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DepositsAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020	Mar. 31, 2019
Loss Contingencies [Line Items]
Settlement days of bond transaction	within one to two trading days
Collateral deposits	$ 2.2		$ 4.1
Subsequent Event [Member]
Loss Contingencies [Line Items]
Collateral deposits		$ 20.8