Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Partnership's contribution to compensation plans	$ 249	$ 213	$ 197
Partnership's contribution to compensation plans by applying mandatory contributions withheld from service partners	$ 36	$ 32

Amount of contributions made by an employer to a defined contribution plan for withholdings from service partners.

No definition available.

Name:	ck0000815917_AmountOfContributionsMadeByEmployerToDefinedContributionPlanForWithholdingsFromServicePartners
Namespace Prefix:	ck0000815917_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration