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		6 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Assets:
Total gains/(losses) (realized and unrealized)	$ 2,400	$ 22,500	$ (17,300)	$ 39,400
Liabilities:
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	5,000	(4,800)	(1,900)	(6,500)
Corporate equity securities [Member]
Liabilities:
Beginning Balance	38	1,015	38	38
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	(977)	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	0	0	0	0
Ending Balance	38	38	38	38
Change in unrealized gains/ (losses) relating to instruments still held	0	558	0	0
Corporate debt securities [Member]
Liabilities:
Beginning Balance	0	0	223	0
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	339	(84)	225	(203)
Purchases	0	(4,082)	(6,677)	(28,319)
Sales	113	3,012	6,804	31,431
Settlements	0	0	0	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	0	3,934	(123)	(129)
Ending Balance	452	2,780	452	2,780
Change in unrealized gains/ (losses) relating to instruments still held	(339)	84	(339)	203
Net derivatives [Member]
Liabilities:
Beginning Balance	3,314	5,773	(4,638)	6,905
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(4,912)	9,485	1,925	11,591
Purchases	(11,963)	(2,150)	(8,848)	(179)
Sales	0	2,149	120	(21)
Settlements	12,078	25	8,395	318
Issuances	389		1,460	0
Net transfers into/ (out of) Level 3	(492)	0	0	(3,332)
Ending Balance	(1,586)	15,282	(1,586)	15,282
Change in unrealized gains/ (losses) relating to instruments still held	4,912	(9,485)	(3,586)	(11,591)
Loans [Member]
Liabilities:
Beginning Balance	9,327	10,260	14,450	22,462
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(332)	62	(277)	754
Purchases	(1,170)	(9,629)	(759)	(22,491)
Sales	350	18,995	350	27,908
Settlements	2,557	139	0	139
Issuances	0		0	0
Net transfers into/ (out of) Level 3	0	11,707	(3,032)	2,762
Ending Balance	10,732	31,534	10,732	31,534
Change in unrealized gains/ (losses) relating to instruments still held	332	(57)	277	(57)
Other secured financings [Member]
Liabilities:
Beginning Balance	65,602	30,394	30,825	8,711
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	0	0	0
Purchases	0	(992)	0	0
Sales	0	0	0	0
Settlements	(9,542)	(9,114)	(11,760)	(9,114)
Issuances	0		36,995	20,691
Net transfers into/ (out of) Level 3	0	0	0	0
Ending Balance	56,060	20,288	56,060	20,288
Change in unrealized gains/ (losses) relating to instruments still held	0	0	0	0
Embedded conversion option [Member]
Liabilities:
Beginning Balance	825	7,607	693	9,574
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(100)	(3,712)	32	(5,679)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	0	0	0	0
Ending Balance	725	3,895	725	3,895
Change in unrealized gains/ (losses) relating to instruments still held	100	3,712	(32)	5,679
Corporate equity securities [Member]
Assets:
Beginning Balance	18,210	12,341	20,964	9,884
Total gains/(losses) (realized and unrealized)	8,030	(178)	7,066	(1,583)
Purchases	0	90	1,469	608
Sales	(73)	(84)	(262)	(370)
Settlements	0	0	0	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	(5,620)	4,233	(8,690)	7,863
Ending Balance	20,547	16,402	20,547	16,402
Change in unrealized gains/(losses) relating to instruments still held	8,073	(178)	7,077	(494)
Corporate debt securities [Member]
Assets:
Beginning Balance	24,795	29,315	22,766	25,666
Total gains/(losses) (realized and unrealized)	(532)	5,659	(796)	5,116
Purchases	2,183	1,937	3,095	3,835
Sales	(2,368)	(5,831)	(3,445)	(3,224)
Settlements	0	0	0	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	7,839	568	10,297	255
Ending Balance	31,917	31,648	31,917	31,648
Change in unrealized gains/(losses) relating to instruments still held	(922)	7,999	(929)	7,420
Collateralized debt obligations [Member]
Assets:
Beginning Balance	96,837	66,028	124,650	37,216
Total gains/(losses) (realized and unrealized)	(5,120)	4,706	(17,229)	14,169
Purchases	29,021	19,146	66,246	36,200
Sales	(25,430)	(49,636)	(59,532)	(55,963)
Settlements	0	(331)	(147)	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	(6,301)	2,400	(24,981)	10,691
Ending Balance	89,007	42,313	89,007	42,313
Change in unrealized gains/(losses) relating to instruments still held	(2,328)	238	(8,989)	5,656
Sovereign obligations [Member]
Assets:
Beginning Balance	333
Total gains/(losses) (realized and unrealized)	(12)
Purchases	320
Sales	(641)
Settlements	0
Issuances	0
Net transfers into/ (out of) Level 3	0
Ending Balance	0		0
Change in unrealized gains/(losses) relating to instruments still held	0
Residential mortgage-backed securities [Member]
Assets:
Beginning Balance	79,953	116,992	82,557	105,492
Total gains/(losses) (realized and unrealized)	(1,820)	(791)	(3,735)	(4,114)
Purchases	8,733	10,955	24,083	21,893
Sales	(4,915)	(24,618)	(18,899)	(37,356)
Settlements	(323)	(459)	(477)	(529)
Issuances	0		0	0
Net transfers into/ (out of) Level 3	7,067	(30,117)	5,166	(13,424)
Ending Balance	88,695	71,962	88,695	71,962
Change in unrealized gains/(losses) relating to instruments still held	315	(422)	(822)	(1,324)
Commercial mortgage-backed securities [Member]
Assets:
Beginning Balance	24,629	17,486	26,655	17,568
Total gains/(losses) (realized and unrealized)	(789)	(903)	(1,124)	(2,191)
Purchases	1,256	18,026	4,685	32,449
Sales	(9,237)	(21,038)	(12,128)	(29,864)
Settlements	(173)	(1,189)	(6,971)	(1,710)
Issuances	0		0	0
Net transfers into/ (out of) Level 3	2,176	11,864	6,745	7,994
Ending Balance	17,862	24,246	17,862	24,246
Change in unrealized gains/(losses) relating to instruments still held	(759)	(1,933)	(496)	(3,236)
Other asset-backed securities [Member]
Assets:
Beginning Balance	7,146	2,375	2,294	12,611
Total gains/(losses) (realized and unrealized)	(19)	(314)	(258)	(537)
Purchases	8,322	15,686	8,385	17,361
Sales	(80)	0	(79)	(5,496)
Settlements	(270)	(438)	(207)	(438)
Issuances	0		0	0
Net transfers into/ (out of) Level 3	(3,242)	28,135	1,722	21,943
Ending Balance	11,857	45,444	11,857	45,444
Change in unrealized gains/(losses) relating to instruments still held	41	(314)	(97)	(569)
Loans and other receivables [Member]
Assets:
Beginning Balance	111,410	128,832	97,258	145,890
Total gains/(losses) (realized and unrealized)	(748)	11,933	(5,795)	3,946
Purchases	40,602	42,278	71,865	92,579
Sales	(26,335)	(48,064)	(29,184)	(88,674)
Settlements	(16,314)	(21,482)	(33,895)	(26,685)
Issuances	0		0	0
Net transfers into/ (out of) Level 3	141	25,146	8,507	11,587
Ending Balance	108,756	138,643	108,756	138,643
Change in unrealized gains/(losses) relating to instruments still held	(669)	11,922	(3,166)	3,382
Investments at fair value [Member]
Assets:
Beginning Balance	128,232	82,205	53,224	66,931
Total gains/(losses) (realized and unrealized)	3,380	2,349	4,615	24,601
Purchases	73	5,160	5,270	27,660
Sales	(78)	(3,946)	(427)	(32,648)
Settlements	(264)	0	(541)	0
Issuances	0		0	0
Net transfers into/ (out of) Level 3	0	(6,452)	69,202	(7,228)
Ending Balance	131,343	79,316	131,343	79,316
Change in unrealized gains/(losses) relating to instruments still held	$ 3,482	$ (299)	$ 4,882	$ 21,954