Revenues from contracts with customers (Tables)

12 Months Ended

Sep. 30, 2019

Disaggregation of Revenue [Line Items]

Disaggregation of Revenue [Table Text Block]

	Year Ended September 30,
	2019		2018		2017
Revenues from contracts with clients:
Commission and clearing fees:
Sales-based:
Exchange-traded futures and options	$	144.9	$	163.4	$	129.7
OTC derivative brokerage	32.1		30.3		28.3
Equities and fixed income	16.1		11.2		16.0
Mutual funds	7.5		7.2		7.9
Insurance and annuity products	7.3		5.8		6.0
Other	1.3		0.9		2.0
Total sales-based commission	209.2		218.8		189.9
Trailing:
Mutual funds	12.4		13.2		13.1
Insurance and annuity products	14.4		14.6		14.2
Total trailing commission	26.8		27.8		27.3
Clearing fees	118.8		123.3		88.5
Trade conversion fees	7.5		6.8		—
Other	10.1		15.1		12.9
Total commission and clearing fees:	372.4		391.8		318.6
Consulting, management, and account fees:
Underwriting fees	0.7		1.7		2.3
Asset management fees	26.2		24.8		25.7
Advisory and consulting fees	20.0		19.0		17.7
Sweep program fees	16.3		11.6		6.0
Client account fees	10.6		11.1		10.8
Other	5.8		2.9		2.5
Total consulting, management, and account fees	79.6		71.1		65.0
Total revenues from contracts with clients	$	452.0	$	462.9	$	383.6
Method of revenue recognition:
Point-in-time	$	362.7	$	379.7	$	306.9
Time elapsed	89.3		83.2		76.7
Total revenues from contracts with clients	452.0		462.9		383.6
Other sources of revenues
Physical precious metals trading	30,694.5		25,762.9		28,018.4
Physical agricultural and energy product trading	1,135.8		919.5		654.9
Principal gains, net	415.8		354.1		297.0
Interest income	198.9		123.3		69.7
Total revenues	$	32,897.0	$	27,622.7	$	29,423.6