Income Taxes - Schedule of Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 597,286	$ 674,088
Depreciation	81,999	99,455
Deferred revenue	56,004	56,651
Allowance for doubtful accounts	21,413	25,525
Deferred compensation	30,818	42,684
Unrealized loss	74,972	56,857
Nondeductible reserves	41,160	40,001
Interest	17,652	17,457
Other	0	923
Total deferred tax assets	921,304	1,013,641
Deferred tax liabilities:
Investment in subsidiaries	97,208	101,437
Amortization of intangible assets	253,147	295,410
Deferred Tax Liabilities, Other	1,829	0
Total deferred tax liabilities	352,184	396,847
Net deferred tax assets	569,120	616,794
Valuation allowance for net deferred tax assets	(650,191)	(711,767)
Net deferred tax liabilities	$ (81,071)	$ (94,973)