Fair Value Disclosures - Summary of Changes in Fair Value of Financial Assets and Liabilities Classified as Level 3 (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Aug. 31, 2015	Aug. 31, 2014	Aug. 31, 2015	Aug. 31, 2014
Assets:
Total gains/(losses) (realized and unrealized)	$ 64,900	$ (6,000)	$ 48,500	$ 19,100
Liabilities:
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	1,700	4,200	(2,300)	(2,000)
Corporate equity securities [Member]
Liabilities:
Beginning Balance	38	38	38	38
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	(38)	0	(38)	0
Ending Balance	0	38	0	38
Change in unrealized gains/ (losses) relating to instruments still held	0	0	0	0
Corporate debt securities [Member]
Liabilities:
Beginning Balance	452	2,780	223	0
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(226)	(101)	(1)	163
Purchases	0	(2,566)	(6,677)	(7)
Sales	0	0	6,804	97
Settlements	0	0	0	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	0	129	(123)	(11)
Ending Balance	226	242	226	242
Change in unrealized gains/ (losses) relating to instruments still held	226	67	(226)	(163)
Net derivatives [Member]
Liabilities:
Beginning Balance	(1,586)	15,282	(4,638)	6,905
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(1,020)	(1,632)	3,022	9,959
Purchases	(1,432)	(74)	(4,527)	(124)
Sales	11,618	74	11,340	(76)
Settlements	24	(70)	(30)	248
Issuances	416	0	1,901	0
Net transfers into/ (out of) Level 3	(857)	0	95	(3,332)
Ending Balance	7,163	13,580	7,163	13,580
Change in unrealized gains/ (losses) relating to instruments still held	551	70	(5,211)	0
Loans [Member]
Liabilities:
Beginning Balance	10,732	31,534	14,450	22,462
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	109	0	(102)	0
Purchases	(3,012)	(16,307)	(3,487)	(15,472)
Sales	0	0	0	3,549
Settlements	0	0	0	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	2,542	(8,566)	(490)	(3,878)
Ending Balance	10,371	6,661	10,371	6,661
Change in unrealized gains/ (losses) relating to instruments still held	(110)	0	102	(10,519)
Other secured financings [Member]
Liabilities:
Beginning Balance	56,060	20,288	30,825	8,711
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(3,914)	(7,570)	(15,674)	(16,684)
Issuances	0	18,948	36,995	39,639
Net transfers into/ (out of) Level 3	(51,572)	0	(51,572)	0
Ending Balance	574	31,666	574	31,666
Change in unrealized gains/ (losses) relating to instruments still held	0	0	0	0
Embedded conversion option [Member]
Liabilities:
Beginning Balance	725	3,895	693	9,574
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(611)	(2,463)	(579)	(8,142)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	0	0	0	0
Ending Balance	114	1,432	114	1,432
Change in unrealized gains/ (losses) relating to instruments still held	611	2,463	579	8,142
Corporate equity securities [Member]
Assets:
Beginning Balance	20,547	16,402	20,964	9,884
Total gains/(losses) (realized and unrealized)	3,901	(480)	10,247	(1,528)
Purchases	21,162	4,528	22,631	36,661
Sales	(5,173)	(529)	(5,176)	(31,444)
Settlements	0	0	0	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	(1,935)	(12,144)	(10,164)	(5,796)
Ending Balance	38,502	7,777	38,502	7,777
Change in unrealized gains/(losses) relating to instruments still held	3,803	(286)	10,210	(400)
Corporate debt securities [Member]
Assets:
Beginning Balance	31,917	31,648	22,766	25,666
Total gains/(losses) (realized and unrealized)	(5,276)	5,454	(5,425)	10,727
Purchases	10,395	21,793	83,613	137,164
Sales	(17,197)	(15,713)	(88,711)	(128,733)
Settlements	(1)	(34)	(1)	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	4,493	(6,264)	12,089	(7,940)
Ending Balance	24,331	36,884	24,331	36,884
Change in unrealized gains/(losses) relating to instruments still held	(5,544)	3,470	(5,797)	10,177
Collateralized debt obligations [Member]
Assets:
Beginning Balance	89,007	42,313	124,650	37,216
Total gains/(losses) (realized and unrealized)	(12,560)	(845)	(28,999)	5,198
Purchases	14,961	7,613	63,038	94,743
Sales	0	(15,204)	(47,570)	(99,661)
Settlements	(13,230)	0	(20,481)	0
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	2,872	9,863	(9,588)	6,244
Ending Balance	81,050	43,740	81,050	43,740
Change in unrealized gains/(losses) relating to instruments still held	(12,561)	(1,575)	(22,654)	(6,283)
U.S. government and federal agency securities [Member]
Assets:
Beginning Balance		0		0
Total gains/(losses) (realized and unrealized)		(11)		(11)
Purchases		2,505		2,505
Sales		0		0
Settlements		0		0
Issuances		0		0
Net transfers into/ (out of) Level 3		0		0
Ending Balance		2,494		2,494
Change in unrealized gains/(losses) relating to instruments still held		(11)		(11)
Residential mortgage-backed securities [Member]
Assets:
Beginning Balance	88,695	71,962	82,557	105,492
Total gains/(losses) (realized and unrealized)	(3,009)	(2,557)	(6,776)	(6,974)
Purchases	10,034	3,981	30,865	44,454
Sales	(8,424)	(9,635)	(25,222)	(65,229)
Settlements	(195)	(325)	(358)	(812)
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	(679)	17,608	5,356	4,103
Ending Balance	86,422	81,034	86,422	81,034
Change in unrealized gains/(losses) relating to instruments still held	655	(302)	(2,507)	(3,564)
Commercial mortgage-backed securities [Member]
Assets:
Beginning Balance	17,862	24,246	26,655	17,568
Total gains/(losses) (realized and unrealized)	(510)	(256)	(2,053)	(3,120)
Purchases	0	641	3,366	34,959
Sales	(680)	(7,068)	(9,973)	(32,774)
Settlements	0	0	(6,981)	(1,315)
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	(1,525)	1,764	4,133	4,009
Ending Balance	15,147	19,327	15,147	19,327
Change in unrealized gains/(losses) relating to instruments still held	(545)	(832)	(1,851)	(3,380)
Other asset-backed securities [Member]
Assets:
Beginning Balance	11,857	45,444	2,294	12,611
Total gains/(losses) (realized and unrealized)	870	1,272	666	256
Purchases	21,913	50,620	69,892	52,495
Sales	0	(49,411)	(40,000)	(52,282)
Settlements	(1,167)	(8,774)	(1,438)	(8,804)
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	(877)	(37,072)	1,182	(2,197)
Ending Balance	32,596	2,079	32,596	2,079
Change in unrealized gains/(losses) relating to instruments still held	813	(3)	607	0
Loans and other receivables [Member]
Assets:
Beginning Balance	108,756	138,643	97,258	145,890
Total gains/(losses) (realized and unrealized)	(2,111)	(8,074)	(7,331)	(9,028)
Purchases	31,269	194,387	115,370	247,383
Sales	(603)	(96,340)	(40,978)	(147,851)
Settlements	(42,529)	(40,617)	(82,100)	(61,791)
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	617	26	13,180	13,422
Ending Balance	95,399	188,025	95,399	188,025
Change in unrealized gains/(losses) relating to instruments still held	(6,182)	(7,967)	(8,850)	(8,961)
Investments at fair value [Member]
Assets:
Beginning Balance	131,343	79,316	53,224	66,931
Total gains/(losses) (realized and unrealized)	83,580	(512)	88,195	23,615
Purchases	0	500	0	28,160
Sales	(127,427)	(5,414)	(124,854)	(38,062)
Settlements	(277)	(305)	(3,818)	(945)
Issuances	0	0	0	0
Net transfers into/ (out of) Level 3	(21,010)	5,416	53,462	(698)
Ending Balance	66,209	79,001	66,209	79,001
Change in unrealized gains/(losses) relating to instruments still held	$ 19,675	$ (403)	$ 24,372	$ 9,126