Fair Value - Partnership's Financial Assets at Fair Value (Detail) - USD ($) $ in Millions | Sep. 25, 2015 | Dec. 31, 2014 |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | $ 2,055 | $ 1,334 |
Investment securities: | | |
Total investment securities | 188 | 161 |
Inventory securities: | | |
Total inventory securities | 67 | 69 |
Mutual Funds [Member] | | |
Investment securities: | | |
Total investment securities | 179 | 136 |
Inventory securities: | | |
Total inventory securities | 5 | 5 |
Government and Agency Obligations [Member] | | |
Investment securities: | | |
Total investment securities | 4 | 19 |
Other [Member] | | |
Inventory securities: | | |
Total inventory securities | | 2 |
U.S. Treasuries [Member] | | |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | 1,805 | 1,109 |
State and Municipal Obligations [Member] | | |
Inventory securities: | | |
Total inventory securities | 32 | 40 |
Equities [Member] | | |
Investment securities: | | |
Total investment securities | 4 | 5 |
Inventory securities: | | |
Total inventory securities | 17 | 17 |
Corporate Bonds and Notes [Member] | | |
Investment securities: | | |
Total investment securities | 1 | 1 |
Inventory securities: | | |
Total inventory securities | 3 | 2 |
Certificates of Deposit [Member] | | |
Cash equivalents: | | |
Cash and cash equivalents | 150 | 100 |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | 250 | 225 |
Inventory securities: | | |
Total inventory securities | 10 | 3 |
Level I [Member] | | |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | 1,805 | 1,109 |
Investment securities: | | |
Total investment securities | 187 | 160 |
Inventory securities: | | |
Total inventory securities | 22 | 23 |
Level I [Member] | Mutual Funds [Member] | | |
Investment securities: | | |
Total investment securities | 179 | 136 |
Inventory securities: | | |
Total inventory securities | 5 | 5 |
Level I [Member] | Government and Agency Obligations [Member] | | |
Investment securities: | | |
Total investment securities | 4 | 19 |
Level I [Member] | Other [Member] | | |
Inventory securities: | | |
Total inventory securities | | 1 |
Level I [Member] | U.S. Treasuries [Member] | | |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | 1,805 | 1,109 |
Level I [Member] | Equities [Member] | | |
Investment securities: | | |
Total investment securities | 4 | 5 |
Inventory securities: | | |
Total inventory securities | 17 | 17 |
Level II [Member] | | |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | 250 | 225 |
Investment securities: | | |
Total investment securities | 1 | 1 |
Inventory securities: | | |
Total inventory securities | 45 | 46 |
Level II [Member] | Other [Member] | | |
Inventory securities: | | |
Total inventory securities | | 1 |
Level II [Member] | State and Municipal Obligations [Member] | | |
Inventory securities: | | |
Total inventory securities | 32 | 40 |
Level II [Member] | Corporate Bonds and Notes [Member] | | |
Investment securities: | | |
Total investment securities | 1 | 1 |
Inventory securities: | | |
Total inventory securities | 3 | 2 |
Level II [Member] | Certificates of Deposit [Member] | | |
Cash equivalents: | | |
Cash and cash equivalents | 150 | 100 |
Investments segregated under federal regulations: | | |
Total investments segregated under federal regulations | 250 | 225 |
Inventory securities: | | |
Total inventory securities | $ 10 | $ 3 |