Investment in Unconsolidated Affiliates (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments in and Advances to Affiliates [Line Items]
Company's share in the earnings of LSV	$ 159,791	$ 152,550	$ 126,103
Distributions received from LSV	$ 166,941	143,517	125,224
LSV Asset Management
Investments in and Advances to Affiliates [Line Items]
Ownership interest in LSV	38.90%
Total investment in LSV	$ 52,342
Company's share in the earnings of LSV	159,791	152,550	126,103
Distributions received from LSV	$ 166,941	$ 143,517	$ 125,224
Maximum
Investments in and Advances to Affiliates [Line Items]
Ownership interest in LSV	50.00%

Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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