Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document Information [Table] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Document Information [Line Items] Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Trading Symbol Entity Common Stock, Shares Outstanding Entity Shell Company Entity Emerging Growth Company Entity Small Business Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Series A Preferred Stock [Member] Series A Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Assets [Abstract] Assets Assets Total assets Cost Method Investments Investments, carried at cost (Note 9) Investments, carried at cost Carrying value of investmet Goodwill Goodwill (Note 24) Beginning balance Ending balance Notes, Loans and Financing Receivable, Net, Noncurrent Note receivable, net (Note 8) Total note receivable, net Other Assets, Noncurrent Other noncurrent assets Property, Plant and Equipment, Net Fixed assets, net Total Debt Securities, Held-to-maturity, Noncurrent Securities held-to-maturity Deferred Tax Assets, Net, Noncurrent Deferred tax assets, net Indemnification Receivable Noncurrent Indemnification receivable (Note 22) Indemnification receivable noncurrent. Current assets: Accounts Receivable, Net, Current Accounts receivable Assets, Current Total current assets Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Cash and cash equivalents—beginning of year Cash and cash equivalents—end of year Other Assets, Current Other current assets Prepaid Expense, Current Prepaid expenses Security Owned and Sold, Not yet Purchased Fair Value, Security Owned Securities owned, at fair value Securities Owned Total Debt Securities, Held-to-maturity, Current Securities held-to-maturity Income Taxes Receivable, Current Income taxes receivable Indefinite-lived Intangible Assets (Excluding Goodwill) Intangible assets (Note 24) Intangible asset related to its customary advisory agreement Beginning balance Ending balance Liabilities and stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity Liabilities [Abstract] Liabilities Current liabilities: Accounts Payable and Other Accrued Liabilities, Current Accounts payable and other liabilities Accounts Payable, Trade, Current Fund management and administration payable Liabilities, Current Total current liabilities Liabilities Total liabilities Deferred Rent Credit, Noncurrent Deferred rent payable Employee-related Liabilities, Current Compensation and benefits payable Security Owned and Sold, Not yet Purchased Fair Value, Security Sold, Not yet Purchased Securities sold, but not yet purchased, at fair value Securities Sold, but not yet Purchased Total Deferred Consideration Noncurrent Deferred consideration—gold payments (Note 11) Deferred consideration, non-current Deferred consideration - noncurrent. Long-term Debt Long-term debt (Note 12) Deferred Consideration Current Deferred consideration—gold payments (Note 11) Deferred consideration, current Deferred Consideration Current Unrecognized Tax Benefits And Interest And Penalties Other noncurrent liabilities (Note 22) Accrued for unrecognized tax benefits and interest/penalties related to a tax position claimed or expected to be claimed on a tax return Ending balance Accrued for unrecognized tax benefits and interest/penalties related to a tax position claimed or expected to be claimed on a tax return. Stockholders' equity Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income Additional Paid in Capital, Common Stock Additional paid-in capital Common Stock, Value, Issued Common stock, par value $0.01; 250,000 shares authorized; issued and outstanding: 153,202 and 136,996 at December 31, 2018 and December 31, 2017, respectively Preferred Stock, Value, Issued Preferred stock, par value $0.01; 2,000 shares authorized: Retained Earnings (Accumulated Deficit) Accumulated deficit Stockholders' Equity Attributable to Parent Total stockholders' equity Balance Balance Commitments and Contingencies Commitments and Contingencies (Note 14) Preferred stock – Series A Non-Voting Convertible, par value $0.01; 14.750 shares authorized, issued and outstanding (Note 13) Preferred stock—Series A Non-Voting Convertible, par value $0.01; 14.750 shares authorized, issued and outstanding (Note 13) Preferred Shares—carrying value Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Balance, shares Balance, shares Temporary Equity, Par or Stated Value Per Share Preferred stock, par value Temporary Equity, Shares Authorized Preferred stock, shares authorized Preferred stock, shares issued Preferred stock, shares outstanding Preferred Stock, Par or Stated Value Per Share Preferred stock, par value Preferred Stock, Shares Authorized Preferred stock, shares authorized Income Statement [Abstract] Common Stock, Dividends, Per Share, Declared Cash dividends declared per common share Income Tax Expense (Benefit) Income tax expense Income tax expense Net Income (Loss) Attributable to Parent Net income Net income Net income Operating Expenses [Abstract] Operating Expenses: Business Development Sales and business development Communications, Information Technology and Occupancy Occupancy, communications and equipment Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization Cost of Goods and Services Sold Fund management and administration Professional Fees Professional and consulting fees Labor and Related Expense Compensation and benefits Marketing and Advertising Expense Marketing and advertising Other Expenses Other Third Party Distribution Third-party distribution fees Third Party Distribution. Contractual gold payments (Note 11) Contractual gold payments Contractual gold payments Contractual gold payments. Operating Income (Loss) Operating income Operating losses Operating Expenses Total expenses Total operating expenses Business Combination, Acquisition Related Costs Acquisition-related costs (Note 3) Acquisition related costs Nonoperating Income (Expense) [Abstract] Other Income/(Expenses): Other income/(expenses) Investment Income, Interest Interest income Other gains and losses, net Other losses, net Other gains/(losses), net Interest expense Interest expense Interest expense Gain on revaluation of deferred consideration – gold payments (Note 5) Gain on revaluation of deferred consideration—gold payments (Note 5) Gain on revaluation of deferred consideration Gain (loss) on revaluation of deferred consideration Gain on revaluation of deferred consideration Gain/loss on revaluation of deferred consideration Gain on revaluation of deferred consideration Gain/loss from revaluation of deferred consideration. Gain (Loss) Related to Litigation Settlement Settlement gain (Note 9) Settlement gain Settlement gain Asset Impairment Charges Impairments (Note 25) Impairments Impairment charges Pre-tax capital loss Business Combination Acquisition Related Expense Acquisition payment Acquisition payment Acquisition payment The amount of expense recognized in business combination. Weighted Average Number of Shares Outstanding, Diluted Weighted-average common shares-diluted Weighted average diluted shares Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before taxes Income/(loss) before taxes Earnings Per Share, Basic Earnings per share-basic Basic earnings per share Earnings Per Share, Diluted Earnings per share-diluted Diluted earnings per share Weighted Average Number of Shares Outstanding, Basic Weighted-average common shares-basic Weighted average common shares (in thousands) Weighted average common shares Revenues [Abstract] Operating Revenues: Revenues Total revenues Total revenues (currently reported) Total operating revenues Product and Service [Axis] Product and Service [Domain] Other Services Income [Member] Other Income [Member] Other Income [Member] Investment Advisory, Management and Administrative Service [Member] Advisory Fees [Member] Advisory Fees [Member] Statement of Comprehensive Income [Abstract] Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive income/(loss) Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Change in unrealized gains/(losses) on available-for-sale debt securities, net of tax Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Foreign currency translation adjustment Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Other comprehensive income Other comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income Statement of Partners' Capital [Abstract] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Loss [Member] Additional Paid-in Capital [Member] Additional Paid-In Capital [Member] Common Stock [Member] Common Stock [Member] Retained Earnings [Member] Accumulated Deficit [Member] Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation Tax benefit from stock option exercised and vested restricted shares Dividends Dividends Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Restricted stock issued net, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercise of stock options net, shares Options, Exercised Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Restricted stock issued, net Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Stock-based compensation Stock Issued During Period, Value, Stock Options Exercised Exercise of stock options, net Stock Repurchased During Period, Shares Shares repurchased, shares Repurchased common stock, shares Stock Repurchased During Period, Value Shares repurchased Repurchased common stock, value Stock Issued During Period, Value, New Issues Common stock issued Stock Issued During Period, Shares, New Issues Common stock issued, shares Statement of Cash Flows [Abstract] Cash and Cash Equivalents, Period Increase (Decrease) Net increase/(decrease) in cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents, Continuing Operations (Decrease)/increase in cash flow due to changes in foreign exchange rate Supplemental Cash Flow Information [Abstract] Supplemental disclosure of cash flow information: Income Taxes Paid, Net Cash paid for taxes Cash paid for interest Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Goodwill, Impairment Loss Impairments Deferred Income Tax Expense (Benefit) Deferred income taxes Share-based Compensation Stock-based compensation Stock-based compensation expense Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities, net of the effects of the ETFS Acquisition: Increase (Decrease) in Accounts Receivable Accounts receivable Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability Acquisition payable Increase (Decrease) in Accounts Payable and Other Operating Liabilities Accounts payable and other liabilities Increase (Decrease) in Employee Related Liabilities Compensation and benefits payable Increase (Decrease) in Financial Instruments Sold, Not yet Purchased Securities sold, but not yet purchased, at fair value Increase (Decrease) in Financial Instruments Used in Operating Activities Securities owned, at fair value Increase Decrease in Fund Management and Administration Payable Fund management and administration payable Increase (decrease) in fund management and administration payable. Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable Income taxes receivable/payable Increase (Decrease) in Other Operating Assets Other assets Increase (Decrease) in Prepaid Expense Prepaid expenses Gold and other precious metals Gold and other precious metals Cash realized upon sale of gold and other precious metals. Other Noncash Income (Expense) Other Advisory fees paid in gold and other precious metals Advisory fees paid in gold. Paid-in-kind interest income (Note 8) Paid-in-kind interest income (Note 8) Interest income recognized Paid-in-kind interest income. Amortization of credit facility issuance costs Net Cash Provided by (Used in) Operating Activities Net cash provided by operating activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities: Payments for Repurchase of Common Stock Shares repurchased Payments of Dividends Dividends paid Proceeds from Stock Options Exercised Proceeds from exercise of stock options Cash received from option exercise Net Cash Provided by (Used in) Financing Activities Net cash provided by/(used in) financing activities Credit facility issuance costs Credit facility issuance costs Preferred stock issuance costs Preferred stock issuance costs Proceeds from the issuance of long-term debt (Note 12) Proceeds from term loan Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities: Payments to Acquire Debt Securities, Available-for-sale Purchase of debt securities available-for-sale Payments to Acquire Held-to-maturity Securities Purchase of securities held-to-maturity Payments to Acquire Investments Purchase of investments Payments to Acquire Notes Receivable Funding of AdvisorEngine note receivable (Note 8) Payments to Acquire Property, Plant, and Equipment Purchase of fixed assets Proceeds from Sale and Maturity of Debt Securities, Available-for-sale Proceeds from sales and maturities of debt securities available-for-sale Proceeds from sale and maturity of available-for-sale securities Proceeds from Sale, Maturity and Collection of Investments Proceeds from held-to-maturity securities maturing or called prior to maturity Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Cash paid – ETFS Acquisition, net of cash acquired (Note 3) Cash paid—ETFS Acquisition, net of cash acquired (Note 3) Payments to Acquire Business Two, Net of Cash Acquired Cash paid—Acquisition of the right to manage Questrade's ETFs (Note 24) Payments to Acquire Business Three, Net of Cash Acquired Cash paid—Managing owner of GCC, net of cash acquired (Note 24) Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Convertible Preferred Stock [Member] Convertible Preferred Stock [Member] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain]