SEGMENT INFORMATION, Classified by Major Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Revenues:
Total revenues	$ 1,340,918	$ 1,312,624	$ 2,642,444	$ 2,592,468
Pre-tax income excluding noncontrolling interests
Pre-tax income excluding noncontrolling interests	198,118	180,320	366,456	383,228
Total assets:
Total assets	27,753,211		27,753,211			$ 26,479,684
Goodwill:
Goodwill	313,005	295,486	313,005	295,486	$ 307,635	307,635	$ 295,486	$ 295,486
United States
Revenues:
Total revenues	1,244,610	1,214,397	2,449,529	2,395,705
Pre-tax income excluding noncontrolling interests
Pre-tax income excluding noncontrolling interests	191,210	176,602	353,069	378,787
Total assets:
Total assets	25,437,969		25,437,969			24,543,645
Goodwill:
Goodwill	275,000		275,000			275,000
Canada
Revenues:
Total revenues	62,466	69,581	124,315	137,293
Pre-tax income excluding noncontrolling interests
Pre-tax income excluding noncontrolling interests	4,124	5,262	9,194	7,487
Total assets:
Total assets	2,235,058		2,235,058			1,814,178
Goodwill:
Goodwill	38,000		38,000			33,000
Europe
Revenues:
Total revenues	21,382	21,211	44,915	45,125
Pre-tax income excluding noncontrolling interests
Pre-tax income excluding noncontrolling interests	(897)	(1,970)	(1,343)	(3,726)
Total assets:
Total assets	29,967		29,967			36,669
Other
Revenues:
Total revenues	12,460	7,435	23,685	14,345
Pre-tax income excluding noncontrolling interests
Pre-tax income excluding noncontrolling interests	3,681	$ 426	5,536	$ 680
Total assets:
Total assets	$ 50,217		$ 50,217			$ 85,192