Offsetting Assets and Liabilities - Schedule of Partnership's Securities Purchased Under Agreement to Resell (Parenthetical) (Detail)	Dec. 31, 2018	Dec. 31, 2017
United States [Member]
Offsetting Assets And Liabilities [Line Items]
Actual collateral of related assets	102.00%	102.00%
Canada [Member]
Offsetting Assets And Liabilities [Line Items]
Actual collateral of related assets	100.00%	100.00%

Securities purchased under agreements to resell fair value of underlying collateral percentage.

No definition available.

Name:	ck0000815917_SecuritiesPurchasedUnderAgreementsToResellFairValueOfUnderlyingCollateralPercentage
Namespace Prefix:	ck0000815917_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant