Discontinued Operations previously held for sale Schedule of Financial Results of DMG's Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) On Disposition Of Business Interests Before Tax			$ (16,252)	$ (23,022)
Net (loss) income from discontinued operations, net of tax	$ 0	$ (6,843)	9,980	102,854
DMG held for sale | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	0	0	0	2,713,059
Expenses	0	1,996	0	2,541,783
(Loss) income from discontinued operations before taxes	0	(1,996)	0	171,276
Gain (Loss) On Disposition Of Business Interests Before Tax	0	0		(23,022)	$ (23,022)
Income tax expense	$ 0	$ 4,847	0	$ 45,400
Coronavirus Aid Relief And Economic Security Act Additional Tax Benefit | DMG held for sale | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (Loss) On Disposition Of Business Interests Before Tax			$ 9,980