Consolidated Statements Of Financial Condition (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Consolidated Statements Of Financial Condition [Abstract]
Cash and cash equivalents	$ 854,054	$ 87,584
Cash and investments segregated under federal regulations	4,099,299	3,614,163
Securities purchased under agreements to resell	413,169	955,209
Receivable from:
Customers	2,350,697	2,318,306
Brokers, dealers and clearing organizations	232,624	239,520
Mutual funds, insurance companies and other	152,129	142,480
Securities owned, at fair value:
Inventory securities	86,865	81,175
Investment securities	99,964	93,411
Equipment, property and improvements, at cost, net of accumulated depreciation and amortization	588,728	615,036
Other assets	93,516	94,266
TOTAL ASSETS	8,971,045	8,241,150
Payable to:
Customers	6,144,402	5,606,760
Brokers, dealers and clearing organizations	94,584	59,233
Securities sold, not yet purchased, at fair value	6,673	6,704
Accrued compensation and employee benefits	561,373	506,221
Accounts payable and accrued expenses	152,297	187,162
Long-term debt	25,432	66,397
Total liabilities before subordinated to claims of general creditors	6,984,761	6,432,477
Liabilities subordinated to claims of general creditors	150,000	203,700
Commitments and contingencies (See Note 8)
Partnership capital subject to mandatory redemption, net of reserve for anticipated withdrawals	1,747,108	1,496,725
Reserve for anticipated withdrawals	89,176	108,248
Total partnership capital subject to mandatory redemption	1,836,284	1,604,973
TOTAL LIABILITIES	$ 8,971,045	$ 8,241,150