Held for Sale and Discontinued Operations - Schedule of Financial Results for DMG's Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairment charges									$ 36,196	$ 28,415	$ 4,066
Net loss from discontinued operations, net of tax	$ 143,587	$ (370,872)	$ (24,520)	$ 6,433	$ 11,772	$ 20,213	$ (118,443)	$ (71,804)	(237,659)	(152,499)	(53,467)
DMG | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues									4,676,213	4,113,414	3,837,260
Expenses									4,634,782	3,994,624	3,596,342
Goodwill impairment charges									651,659	253,000	206,169
(Loss) income from discontinued operations before taxes									(610,228)	(134,210)	34,749
Income tax benefit (expense)									364,856	(24,052)	(88,216)
Net loss from discontinued operations, net of tax									$ (245,372)	$ (158,262)	$ (53,467)