Schedule I (PARENT COMPANY ONLY) - CONDENSED STATEMENTS OF CASH FLOWS (Details) - USD ($) $ in Thousands	12 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2015
Cash flows from operating activities:
Net earnings	$ 357,498	$ 15,434	$ 93,534
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Amortization	1,977	(2,365)	15,236
(Income) loss on loans to and investments in related parties	(109,395)	(17,184)	(75,717)
Distributions received on investments in related parties	21,038	38,180	76,681
Other adjustments	44,043	(32,711)	(97,804)
Net change in assets and liabilities:
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	280,703	(107,771)	2,691,028
Financial instruments owned	(110,368)	2,529,114	2,003,978
Investments in managed funds	(8,719)	(138,572)	15,498
Other assets	8,435	(173,127)	(62,361)
Financial instruments sold, not yet purchased	(279,282)	1,753,647	(2,043,319)
Accrued expenses and other liabilities	524,304	296,067	(259,665)
Net cash provided by (used in) operating activities	820,486	(121,610)	(238,638)
Cash flows from investing activities:
Cash received from contingent consideration	1,342	2,617	4,444
Net cash provided by (used in) investing activities	9,136	79,758	(134,612)
Cash flows from financing activities:
Proceeds from short-term borrowings	34,499,230	15,313,383	17,263,217
Payments on short-term borrowings	(34,594,992)	(15,108,501)	(16,964,558)
Proceeds from issuance of long-term debt, net of issuance costs	1,116,798	299,779	0
Repayment of long-term debt	(186,444)	(373,246)	(500,000)
Net cash provided by (used in) financing activities	795,474	86,373	(189,943)
Net increase (decrease) in cash and cash equivalents	1,635,423	18,906	(569,805)
Cash and cash equivalents at beginning of period	3,529,069	3,510,163	4,079,968
Cash and cash equivalents at end of period	5,164,492	3,529,069	3,510,163
Cash paid (received) during the period for:
Interest	1,025,576	859,466	859,815
Income taxes, net	8,910	(6,410)	(683)
Parent Company
Cash flows from operating activities:
Net earnings	357,498	15,434	93,534
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Amortization	(61,634)	(63,681)	(76,945)
Undistributed earnings of subsidiaries	(304,520)	(25,804)	(71,739)
(Income) loss on loans to and investments in related parties	(90,724)	10,251	(40,460)
Distributions received on investments in related parties	0	17,050	40,500
Other adjustments	39,513	(34,496)	(98,870)
Net change in assets and liabilities:
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	(21,669)	30,055	(4,714)
Financial instruments owned	77,475	8,704	53,290
Investments in managed funds	12,924	763	19,907
Other assets	(29,031)	21,475	77,813
Financial instruments sold, not yet purchased	10,776	(13,739)	(8,802)
Accrued expenses and other liabilities	324,446	15,125	(36,397)
Net cash provided by (used in) operating activities	315,054	(18,863)	(52,883)
Cash flows from investing activities:
Investments in, advances to and subordinated notes receivable from subsidiaries	(415,100)	327,110	420,797
Loans to and investments in related parties	(73,915)	19,337	(19,301)
Cash received from contingent consideration	1,342	2,617	4,444
Net cash provided by (used in) investing activities	(487,673)	349,064	405,940
Cash flows from financing activities:
Proceeds from short-term borrowings	555,652	102,238	750,000
Payments on short-term borrowings	(532,326)	(5,786)	(750,000)
Proceeds from issuance of long-term debt, net of issuance costs	1,116,798	277,583	0
Repayment of long-term debt	(186,444)	(350,000)	(500,000)
Net cash provided by (used in) financing activities	953,680	24,035	(500,000)
Net increase (decrease) in cash and cash equivalents	781,061	354,236	(146,943)
Cash and cash equivalents at beginning of period	1,178,475	824,239	971,182
Cash and cash equivalents at end of period	1,959,536	1,178,475	824,239
Cash paid (received) during the period for:
Interest	332,135	300,680	329,926
Income taxes, net	$ 2,494	$ (8,654)	$ (5,859)