Goodwill, Deferred Leasing Costs and Other Intangibles - Goodwill By Reportable Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill	$ 1,373,891	$ 1,452,891
Goodwill deductible for tax purposes	140,500	140,500
Digital
Goodwill [Line Items]
Goodwill	777,330	726,330
Other investment management
Goodwill [Line Items]
Goodwill	$ 596,561	$ 726,561