Leucadia Merger and Related Transactions - Assets Acquired and Liabilities Assumed by Major Class (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2013	May 31, 2013	Feb. 28, 2013 Leucadia [Member]	Feb. 28, 2013 Leucadia [Member] Customer relationships [Member]	Feb. 28, 2013 Leucadia [Member] Trade names [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			793,843
Long-term debt			6,362,024
Mandatorily redeemable preferred interests			358,951
Total liabilities			34,646,341
Noncontrolling interests			356,180
Fair value of net assets acquired, excluding goodwill			3,033,721
Goodwill	$ 4,400	$ 4,400	$ 1,720,380