SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Revenues:
Net revenues	$ 2,068	$ 1,859	$ 4,077	$ 3,790
Pre-tax income
Pre-tax income	239	347	598	679
Total assets:
Total assets	49,809		49,809		$ 38,830
Goodwill:
Goodwill	463		463		464
U.S.
Revenues:
Net revenues	1,920	1,729	3,795	3,525
Pre-tax income
Pre-tax income	227	334	579	664
Total assets:
Total assets	46,507		46,507		35,978
Goodwill:
Goodwill	433		433		433
Canada
Revenues:
Net revenues	112	90	207	189
Pre-tax income
Pre-tax income	13	7	21	23
Total assets:
Total assets	3,189		3,189		2,754
Goodwill:
Goodwill	22		22		23
Europe
Revenues:
Net revenues	36	40	75	76
Pre-tax income
Pre-tax income	(1)	6	(2)	$ (8)
Disposition-related expenses for loss on sale of operations		$ 15
Total assets:
Total assets	113		113		98
Goodwill:
Goodwill	$ 8		$ 8		$ 8