Discontinued Operations Gracenote Companies Statement of Operations Footnotes (Details) - USD ($) $ in Thousands		12 Months Ended
	Feb. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of long-term debt		$ 0	$ 703,527	$ 27,842
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	35.00%	35.00%
Gracenote Companies | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued Operations, Tax Effect of Discontinued Operation, Outside Basis Difference				$ 62,000
Effective Income Tax Rate Reconciliation, Discontinued Operations, Percent			48.10%	45.00%
Term B Loans Facility | Amended Secured Credit Facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of long-term debt	$ 400,000