Fair Value Disclosures - Summary of Changes in Fair Value of Financial Assets and Liabilities Classified as Level 3 (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Feb. 28, 2015	Feb. 28, 2014
Assets:
Total gains/(losses) (realized and unrealized)	$ (49,700)	$ 20,300
Liabilities:
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(6,900)	800
Corporate equity securities [Member]
Assets:
Beginning Balance	20,964	9,884
Total gains/(losses) (realized and unrealized)	63	(1,393)
Purchases	0	134
Sales	(168)	0
Settlements	0	0
Issuances	0	0
Net transfers into/ (out of) Level 3	(2,649)	3,716
Ending Balance	18,210	12,341
Change in unrealized gains/(losses) relating to instruments still held	243	(1,319)
Liabilities:
Beginning Balance	38	38
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	8
Purchases	0	0
Sales	0	411
Settlements	0	0
Issuances	0	0
Net transfers into/ (out of) Level 3	0	558
Ending Balance	38	1,015
Change in unrealized gains/ (losses) relating to instruments still held	0	(8)
Corporate debt securities [Member]
Assets:
Beginning Balance	55,918	25,666
Total gains/(losses) (realized and unrealized)	(1,930)	(2,014)
Purchases	469	4,136
Sales	(533)	(624)
Settlements	0	0
Issuances	0	0
Net transfers into/ (out of) Level 3	(23,189)	2,151
Ending Balance	30,735	29,315
Change in unrealized gains/(losses) relating to instruments still held	(1,577)	193
Liabilities:
Beginning Balance	223
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(115)
Purchases	(6,683)
Sales	6,698
Settlements	0
Issuances	0
Net transfers into/ (out of) Level 3	(123)
Ending Balance	0
Change in unrealized gains/ (losses) relating to instruments still held	0
Collateralized debt obligations [Member]
Assets:
Beginning Balance	91,498	37,216
Total gains/(losses) (realized and unrealized)	(16,022)	10,184
Purchases	0	76,511
Sales	(13,519)	(78,081)
Settlements	(1,296)	(144)
Issuances	0	0
Net transfers into/ (out of) Level 3	30,236	20,342
Ending Balance	90,897	66,028
Change in unrealized gains/(losses) relating to instruments still held	(15,886)	5,662
Sovereign obligations [Member]
Assets:
Beginning Balance	0
Total gains/(losses) (realized and unrealized)	13
Purchases	0
Sales	(1)
Settlements	0
Issuances	0
Net transfers into/ (out of) Level 3	321
Ending Balance	333
Change in unrealized gains/(losses) relating to instruments still held	12
Residential mortgage-backed securities [Member]
Assets:
Beginning Balance	82,557	105,492
Total gains/(losses) (realized and unrealized)	(2,863)	(1,626)
Purchases	2,100	9,637
Sales	(1,375)	(13,703)
Settlements	(23)	(1,755)
Issuances	0	0
Net transfers into/ (out of) Level 3	(443)	18,947
Ending Balance	79,953	116,992
Change in unrealized gains/(losses) relating to instruments still held	783	(2,097)
Commercial mortgage-backed securities [Member]
Assets:
Beginning Balance	26,655	17,568
Total gains/(losses) (realized and unrealized)	(531)	(3,032)
Purchases	0	8,933
Sales	(382)	(14,645)
Settlements	(6,864)	(50)
Issuances	0	0
Net transfers into/ (out of) Level 3	5,751	8,712
Ending Balance	24,629	17,486
Change in unrealized gains/(losses) relating to instruments still held	(1,369)	(958)
Other asset-backed securities [Member]
Assets:
Beginning Balance	2,294	12,611
Total gains/(losses) (realized and unrealized)	(167)	72
Purchases	26	2,250
Sales	(1)	(2,048)
Settlements	0	(83)
Issuances	0	0
Net transfers into/ (out of) Level 3	4,994	(10,427)
Ending Balance	7,146	2,375
Change in unrealized gains/(losses) relating to instruments still held	(167)	7
Loans and other receivables [Member]
Assets:
Beginning Balance	97,258	145,890
Total gains/(losses) (realized and unrealized)	(5,033)	(3,902)
Purchases	40,019	36,213
Sales	(16,122)	(49,475)
Settlements	(15,448)	(935)
Issuances	0	0
Net transfers into/ (out of) Level 3	10,736	1,041
Ending Balance	111,410	128,832
Change in unrealized gains/(losses) relating to instruments still held	(3,262)	(3,807)
Investments at fair value [Member]
Assets:
Beginning Balance	95,389	101,242
Total gains/(losses) (realized and unrealized)	1,299	24,889
Purchases	5,010	22,500
Sales	(594)	(29,587)
Settlements	(277)	0
Issuances	0	0
Net transfers into/ (out of) Level 3	69,134	(776)
Ending Balance	169,961	118,268
Change in unrealized gains/(losses) relating to instruments still held	1,304	24,889
Investments in managed funds [Member]
Assets:
Beginning Balance	54,982	57,285
Total gains/(losses) (realized and unrealized)	(24,496)	(2,859)
Purchases	354	5,102
Sales	0	0
Settlements	0	0
Issuances	0	0
Net transfers into/ (out of) Level 3	0	0
Ending Balance	30,840	59,528
Change in unrealized gains/(losses) relating to instruments still held	(24,495)	(2,859)
Net derivatives [Member]
Liabilities:
Beginning Balance	(4,638)	6,905
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	6,938	1,267
Purchases	0	(1,327)
Sales	0	2,169
Settlements	(58)	197
Issuances	1,072	0
Net transfers into/ (out of) Level 3	0	(3,438)
Ending Balance	3,314	5,773
Change in unrealized gains/ (losses) relating to instruments still held	(8,771)	(1,267)
Loans [Member]
Liabilities:
Beginning Balance	14,450	22,462
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	(39)	(153)
Purchases	(2,877)	(18,913)
Sales	825	4,887
Settlements	0	0
Issuances	0	0
Net transfers into/ (out of) Level 3	(3,032)	1,977
Ending Balance	9,327	10,260
Change in unrealized gains/ (losses) relating to instruments still held	39	(153)
Other secured financings at fair value [Member]
Liabilities:
Beginning Balance	30,825	8,711
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	0	0
Purchases	0	0
Sales	0	0
Settlements	(2,218)	0
Issuances	36,995	21,683
Net transfers into/ (out of) Level 3	0	0
Ending Balance	65,602	30,394
Change in unrealized gains/ (losses) relating to instruments still held	0	0
Embedded conversion option [Member]
Liabilities:
Beginning Balance	693	9,574
Net gains/(losses) on Level 3 liabilities (realized and unrealized)	132	(1,967)
Purchases	0	0
Sales	0	0
Settlements	0	0
Issuances	0	0
Net transfers into/ (out of) Level 3	0	0
Ending Balance	825	7,607
Change in unrealized gains/ (losses) relating to instruments still held	$ (132)	$ 0