Held for Sale and Discontinued Operations Schedule of Financial Results of DMG's Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment charges	$ 0	$ 0	$ 3,106	$ 34,696	$ 36,196
Net (loss) income from discontinued operations, net of tax	(211,739)	(370,872)	(147,829)	(388,959)
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	1,252,909	1,178,443	3,733,270	3,461,493
Expenses	1,260,814	1,164,562	3,679,747	3,396,914
Goodwill impairment charges	0	601,040	0	651,659
Valuation Adjustment	98,201	0	98,201	0
(Loss) income from discontinued operations before taxes	(106,106)	(587,159)	(44,678)	(587,080)
Income tax benefit	$ 105,633	$ (216,287)	$ 103,151	$ (198,121)