Fair Value (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Partnership's Financial Assets at Fair Value

The following tables show the Partnership's financial instruments measured at fair value:

	Financial Assets at Fair Value as of
	December 31, 2017
	Level I		Level II		Level III		Total
Cash equivalents:
Certificates of deposit	$	—	$	275	$	—	$	275
Investments segregated under federal regulations:
U.S. treasuries	$	2,399	$	—	$	—	$	2,399
Securities owned:
Investment securities:
Mutual funds(1)	$	252	$	—	$	—	$	252
Government and agency obligations		3		—		—		3
Equities		2		—		—		2
Corporate bonds and notes		—		1		—		1
Total investment securities	$	257	$	1	$	—	$	258
Inventory securities:
State and municipal obligations	$	—	$	24	$	—	$	24
Equities		16		—		—		16
Mutual funds		4		—		—		4
Certificates of deposit		—		4		—		4
Corporate bonds and notes		—		2		—		2
Total inventory securities	$	20	$	30	$	—	$	50

⁽¹⁾ The mutual funds balance consists primarily of securities held to economically hedge future liabilities related to the non-qualified deferred compensation plan.

	Financial Assets at Fair Value as of
	December 31, 2016
	Level I		Level II		Level III		Total
Cash equivalents:
Certificates of deposit	$	—	$	150	$	—	$	150
Investments segregated under federal regulations:
U.S. treasuries	$	3,999	$	—	$	—	$	3,999
Certificates of deposit		—		150		—		150
Total investments segregated under federal    regulations	$	3,999	$	150	$	—	$	4,149
Securities owned:
Investment securities:
Mutual funds(1)	$	209	$	—	$	—	$	209
Government and agency obligations		9		—		—		9
Equities		5		—		—		5
Corporate bonds and notes		—		1		—		1
Total investment securities	$	223	$	1	$	—	$	224
Inventory securities:
Equities	$	17	$	—	$	—	$	17
State and municipal obligations		—		16		—		16
Mutual funds		7		—		—		7
Corporate bonds and notes		—		2		—		2
Other		—		1		—		1
Total inventory securities	$	24	$	19	$	—	$	43