Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities:
Net income	$ 89,105	$ 95,603
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,754	7,742
Amortization of deferred sales commissions	27,018	26,601
Share-based compensation	24,565	22,828
Excess tax benefits from share-based payment arrangements	(2,831)	(7,499)
Gain on sale of available for sale investment securities	(1,697)	(1,986)
Net purchases and sales or maturities of trading securities	(12,277)	71,301
Unrealized gain on trading securities	(3,078)	(962)
Loss on sale and retirement of property and equipment	4,863	49
Deferred income taxes	(4,866)	(662)
Changes in assets and liabilities:
Cash and cash equivalents - restricted	(23,578)	1,219
Receivables from funds and separate accounts	(2,808)	(4,112)
Other receivables	2,688	(14,973)
Other assets	(1,661)	(3,261)
Deferred sales commissions	(28,795)	(33,382)
Accounts payable and payable to investment companies	8,831	6,478
Other liabilities	16,949	7,312
Net cash provided by operating activities	100,182	172,296
Cash flows from investing activities:
Purchases of available for sale investment securities	(15,796)	(79,167)
Proceeds from sales and maturities of available for sale investment securities	11,281	84,053
Additions to property and equipment	(6,354)	(8,351)
Proceeds from sales of property and equipment	35
Net cash used in investing activities	(10,834)	(3,465)
Cash flows from financing activities:
Dividends paid	(42,999)	(34,459)
Repurchase of common stock	(29,323)	(37,663)
Exercise of stock options		4,722
Excess tax benefits from share-based payment arrangements	2,831	7,499
Net cash used in financing activities	(69,491)	(59,901)
Net increase in cash and cash equivalents	19,857	108,930
Cash and cash equivalents at beginning of period	327,083	195,315
Cash and cash equivalents at end of period	$ 346,940	$ 304,245