Leucadia Merger and Related Transactions - Assets Acquired and Liabilities Assumed by Major Class (Detail) (USD $) In Thousands, unless otherwise specified	May 31, 2013	Feb. 28, 2013 Leucadia [Member]	Feb. 28, 2013 Customer relationships [Member] Leucadia [Member]	Feb. 28, 2013 Trade names (intangible assets) [Member] Leucadia [Member]
Assets acquired:
Cash and cash equivalents		$ 3,017,958
Cash and securities segregated		3,728,742
Financial instruments owned, at fair value		16,413,535
Investments in managed funds		59,976
Loans to and investments in related parties		766,893
Securities borrowed		5,315,488
Securities purchased under agreements to resell		3,578,366
Securities received as collateral		25,338
Brokers, dealers and clearing organizations		2,444,085
Customers		1,045,251
Fees, interest and other		225,555
Premises and equipment		192,603
Indefinite-lived intangible exchange memberships and licenses		15,551
Finite-lived intangible assets			136,002	131,299
Other assets		939,600
Total assets		38,036,242
Liabilities assumed:
Short-term borrowings		100,000
Financial instruments sold, not yet purchased, at fair value		9,766,876
Securities loaned		1,902,687
Securities sold under agreements to repurchase		7,976,492
Other secured financings		122,294
Obligation to return securities received as collateral		25,338
Brokers, dealers and clearing organizations		1,787,055
Customers		5,450,781
Accrued expenses and other liabilities		789,449
Long-term debt		6,362,024
Mandatorily redeemable preferred interests		358,951
Total liabilities		34,641,947
Noncontrolling interests		356,180
Fair value of net assets acquired, excluding goodwill		3,038,115
Goodwill	$ 5,300	$ 1,715,986