Variable Interest Entities - Additional Information (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Variable Interest Entities [Line Items]
Total assets of VIEs	$ 917,922
Total liabilities of VIEs	507,445
DMG | Discontinued Operations, Held-for-sale
Variable Interest Entities [Line Items]
Total assets of VIEs	658,684
Total liabilities of VIEs	$ 355,196