Segments - Schedule of Investments in Unconsolidated Subsidiaries by Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Investments in Unconsolidated Subsidiaries	$ 216,174	$ 238,001
Americas [Member]
Segment Reporting Information [Line Items]
Investments in Unconsolidated Subsidiaries	41,446	39,105
EMEA [Member]
Segment Reporting Information [Line Items]
Investments in Unconsolidated Subsidiaries	864	852
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Investments in Unconsolidated Subsidiaries	6,845	6,581
Global Investment Management [Member]
Segment Reporting Information [Line Items]
Investments in Unconsolidated Subsidiaries	77,926	83,430
Development Services [Member]
Segment Reporting Information [Line Items]
Investments in Unconsolidated Subsidiaries	$ 89,093	$ 108,033