Acquisition and Transition Costs and Special Charges	12 Months Ended
Dec. 31, 2018
Business Combinations [Abstract]
Special Charges Acquisition And Transition Costs And Intangible Asset Amortization [Text Block]	Acquisition and Transition Costs and Special Charges Acquisition and Transition Costs The Company recognized $21, $1,673 and $99 for the years ended December 31, 2018, 2017 and 2016, respectively, as Acquisition and Transition Costs incurred in connection with acquisitions, divestitures, and other ongoing business development initiatives. These costs are primarily comprised of professional fees for legal and other services. In addition, acquisition and transition costs in 2016 included the reversal of $733 of a provision for certain settlements previously established in the fourth quarter of 2015. Special Charges The Company recognized $5,012 for the year ended December 31, 2018, as Special Charges incurred related to separation benefits and costs for the termination of certain contracts associated with closing the Company's agency trading platform in the U.K. and separation benefits and related charges associated with the Company's businesses in Mexico, as well as the acceleration of depreciation expense for leasehold improvements in conjunction with the expansion of the Company's headquarters in New York. The Company recognized $25,437 for the year ended December 31, 2017, as Special Charges incurred related to a charge of $7,107 associated with the impairment of goodwill in the Company's Institutional Asset Management reporting unit, a charge of $14,400 associated with the impairment of the Company's former equity method investment in G5, and expenses of $3,930 associated with the transition of certain employees in conjunction with the sale of the Institutional Trust and Independent Fiduciary business of ETC. See Notes 5 and 10 for further information. The Company recognized $8,100 for the year ended December 31, 2016, as Special Charges incurred related to a charge associated with the impairment of the Company's investment in Atalanta Sosnoff. See Note 10 for further information.

Acquisition and Transition Costs and Special Charges

Acquisition and Transition Costs

The Company recognized $21, $1,673 and $99 for the years ended December 31, 2018, 2017 and 2016, respectively, as Acquisition and Transition Costs incurred in connection with acquisitions, divestitures, and other ongoing business development initiatives. These costs are primarily comprised of professional fees for legal and other services. In addition, acquisition and transition costs in 2016 included the reversal of $733 of a provision for certain settlements previously established in the fourth quarter of 2015.

Special Charges

The Company recognized $5,012 for the year ended December 31, 2018, as Special Charges incurred related to separation benefits and costs for the termination of certain contracts associated with closing the Company's agency trading platform in the U.K. and separation benefits and related charges associated with the Company's businesses in Mexico, as well as the acceleration of depreciation expense for leasehold improvements in conjunction with the expansion of the Company's headquarters in New York.

The Company recognized $25,437 for the year ended December 31, 2017, as Special Charges incurred related to a charge of $7,107 associated with the impairment of goodwill in the Company's Institutional Asset Management reporting unit, a charge of $14,400 associated with the impairment of the Company's former equity method investment in G5, and expenses of $3,930 associated with the transition of certain employees in conjunction with the sale of the Institutional Trust and Independent Fiduciary business of ETC. See Notes 5 and 10 for further information.

The Company recognized $8,100 for the year ended December 31, 2016, as Special Charges incurred related to a charge associated with the impairment of the Company's investment in Atalanta Sosnoff. See Note 10 for further information.