SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Detail) (USD $) | | | | |
| 3 Months Ended
Jun. 30, 2008
| 12 Months Ended
Dec. 31, 2009
| 12 Months Ended
Dec. 31, 2008
| 12 Months Ended
Dec. 31, 2007
|
Summary of Significant Accounting Policies (Detail) | | | | |
Schedule of Variable Interest Entities [Text Block] | |
We are not the primary beneficiary, and do not consolidate the accounts, of a high-yield collateralized bond obligation (CBO) that held assets of $21 million at December 31, 2009. This variable interest entity is a non-recourse, limited liability company for which we are the collateral manager and receive related investment advisory fees. We recognized the full impairment of our investment in this CBO in2002and do not expect to recognize any future gains or losses from this investment. | | |
Variable Interest Entity [Line Items] | | | | |
Marketable Securities, Available-for-sale Securities, Policy | | We value our investments in sponsored mutual funds at the quoted closing net asset values, or NAVs, per share of each mutual fund last reported as of the balance sheet date, and generally classify these holdings as available-for-sale. Our investments in marketable debt securities, including mortgage- and other asset-backed securities held by our savings bank subsidiary, are also classified as available-for-sale and reported at fair value. These debt securities are generally traded in the over-the-counter market. Securities with original maturities of one year or more are valued by us based on prices furnished by dealers who make markets in such securities or by an independent pricing service, which considers the yield or price of bonds of comparable quality, coupon, maturity, and type, as well as prices quoted by dealers who make markets in such securities. Securities with original maturities of less than one year generally are valued at amortized cost, which approximates fair value; however, if amortized cost is deemed not to reflect fair value, such securities are valued by us based generally on prices furnished by dealers who make markets in such securities or by an independent pricing service. Our investment valuation policies, methods and sources are the same as those employed by the sponsored mutual funds to price similar investment holdings. Changes in net unrealized security holding gains (losses) on available-for-sale securities are recognized in accumulated other comprehensive income (loss). We review the carrying amount of each investment on a quarterly basis and recognize an impairment charge in non-operating investment income (loss) whenever an unrealized loss is considered other than temporary. A mutual fund holding with an impairment that has persisted daily throughout the six months between quarter-ends is generally presumed to have an other than temporary impairment unless there is persuasive evidence, such as an increase in value subsequent to quarter end, to overcome that presumption. We may also recognize an other than temporary charge if particular circumstances do not warrant our belief that a near-term recovery is possible. | | |
Marketable Securities, Trading Securities, Policy | | We classify some investments in sponsored mutual funds made at fund formation as trading because they are expected to be held for only a short period of time. | | |
Equity and Cost Method Investments, Policy | | Other investments are recognized using the cost or equity methods of accounting, as appropriate. | | |
Concentration Risk, Credit Risk | | Concentration of credit risk in accounts receivable is believed to be minimal in that our clients generally have substantial assets, including those in the investment portfolios that we manage for them. | | |
Concentration Risk, Market Risk | | Our investments in sponsored mutual funds expose us to market risk in the form of equity price risk; that is, the potential future loss of value that would result from a decline in the fair values of the mutual funds. Each fund and its underlying net assets are also subject to market risk, which may arise from changes in equity prices, credit ratings, foreign currency exchange rates, and interest rates. Investments by our savings bank subsidiary in debt securities expose us to market risk, which may arise from changes in credit ratings and interest rates. | | |
Property, Plant and Equipment [Line Items] | | | | |
Management and Investment Advisory Fees, Policy | | Fees for investment advisory services, which are based on a percentage of assets under management, and related administrative services that we provide to investment advisory clients, including our sponsored mutual funds, are recognized in the period that our services are provided. Our assets under management are valued in accordance with a valuation and pricing policy that defines the valuation and pricing processes for each major type of investment held in our sponsored mutual funds and other client investment portfolios. Fair values used in our processes are primarily determined from quoted market prices, prices furnished by dealers who make markets in such securities, or from data provided by an independent pricing service that considers yield or price of investments of comparable quality, coupon, maturity, and type, as well as prices quoted by dealers who make markets in such securities. Investments for which market prices are not readily available are not a material portion of our total assets under management. Administrative revenues from distribution of our sponsored mutual funds' Advisor and R class shares, and the corresponding operating expense for payments to third-party financial intermediaries that distribute those share classes, are recognized in the period that they are earned, which is the same period that the related mutual funds recognize their expense. | | |
Revenue Recognition, Excise and Sales Taxes | | Taxes billed to our clients based on our fees for services rendered are not included in revenues. | | |
Services provided to the sponsored U.S. mutual funds [Text Block] | |
We provide all services to the sponsored U.S. mutual funds under contracts that are subject to periodic review and approval by each of the funds' boards. Regulations require that the funds' shareholders also approve material changes to investment advisory contracts. | | |
Stock-based compensation additional disclosure | | | | |
Weighted-average grant-date fair value per option awarded, including reload grants (in dollars per option) | | 10.07 | 13.51 | 12.31 |
Weighted average expected life in years assumption (in years) | | 6.7 | 5.9 | 5.4 |
Weighted average expected volatility assumption (percentage as a decimal) | | 0.32 | 0.24 | 0.23 |
Weighted average dividend yield assumption (percentage as a decimal) | | 0.024 | 0.017 | 0.017 |
Weighted average risk-free interest rate assumption (percentage as a decimal) | | 0.025 | 0.031 | 0.043 |
Reduction in diluted earnings per share (in dollars per share) | 0.01 | | 0.01 | |
Variable Interest Entity, Not Primary Beneficiary [Member] | | | | |
Variable Interest Entity [Line Items] | | | | |
assets of collateralized bond obligation (in millions of dollars) | | 21 | | |
Restricted shares and restricted stock units under stock incentive plans (2001 and 2004) [Member] | | | | |
Stock-based compensation additional disclosure | | | | |
graded vesting period (in years) | | four to five years | | |
Options under stock incentive plans for employees (1993, 1996, 2001 and 2004) [Member] | | | | |
Stock-based compensation additional disclosure | | | | |
graded vesting period (in years) | | five to six years | | |
maximum term (in years) | | 10 | | |
Options restricted shares and restricted stock units under stock incentive plans for non-employee directors (1995, 1998 and 2007) [Member] | | | | |
Stock-based compensation additional disclosure | | | | |
graded vesting period (in years) | | six months to one year | | |
maximum term (in years) | | 10 | | |
Computer and communications software and equipment [Member] | | | | |
Property, Plant and Equipment [Line Items] | | | | |
Weighted average estimated useful lives (in years) | | 3.5 | | |
Buildings and improvements [Member] | | | | |
Property, Plant and Equipment [Line Items] | | | | |
Weighted average estimated useful lives (in years) | | 32.6 | | |
Leasehold improvements [Member] | | | | |
Property, Plant and Equipment [Line Items] | | | | |
Weighted average estimated useful lives (in years) | | 9.2 | | |
Furniture and other equipment [Member] | | | | |
Property, Plant and Equipment [Line Items] | | | | |
Weighted average estimated useful lives (in years) | | 6.6 | | |
Leased land [Member] | | | | |
Property, Plant and Equipment [Line Items] | | | | |
Weighted average estimated useful lives (in years) | | 99 | | |