Variable Interest Entities - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Variable Interest Entity [Line Items]
Total revenue	$ 132,962	$ 138,752	$ 254,819	$ 243,150
Total costs and expenses	113,292	92,481	242,941	185,043
Operating profit	19,670	46,271	11,878	58,107
Total other income (expense), net	(4,818)	(11,544)	(8,840)	(16,574)
Income before income tax expense (benefit)	14,852	34,727	3,038	41,533
Variable Interest Entity, Primary Beneficiary | GS Holdings
Variable Interest Entity [Line Items]
Total revenue	133,649	138,695	254,819	242,395
Total costs and expenses	115,880	92,189	242,941	184,401
Operating profit	17,769	46,506	11,878	57,994
Total other income (expense), net	(2,937)	(5,377)	(8,944)	(10,059)
Income before income tax expense (benefit)	$ 14,832	$ 41,129	$ 2,934	$ 47,935