Discontinued Operations Gracenote Companies Statement of Operations Footnotes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	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
Effective Income Tax Rate Reconciliation, Discontinued Operations, Percent	48.10%	45.00%	44.00%