Discontinued Operations Gracenote Companies Statement of Operations (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2018	Mar. 31, 2017		Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations, net of taxes		$ 0	$ 15,618
Gracenote Companies | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating revenues	[1],[2]		18,168
Direct operating expenses	[1],[2]		7,292
Selling, general and administrative	[1],[2]		15,349
Operating loss	[1],[2]		(4,473)
Interest income	[1],[2]		16
Interest expense (3)	[1],[2],[3]		(1,261)
Loss before income taxes	[1],[2]		(5,718)
Pretax gain on the disposal of discontinued operations			35,462	[2]	$ 33,000
Total pretax income on discontinued operations	[1],[2]		29,744
Income tax expense (4)	[1],[2],[4]		14,126
Income from discontinued operations, net of taxes	[1],[2]		$ 15,618

[1] (1) Results of operations for the Gracenote Companies are reflected through January 31, 2017, the date of the Gracenote Sale.

[2] (2)No depreciation expense or amortization expense was recorded by the Company in 2017 as the Gracenote Companies’ assets were held for sale as of December 31, 2016.

[3] (3) The Company used $400 million of proceeds from the Gracenote Sale to prepay a portion of its outstanding borrowings under the Company’s Term Loan Facility (as defined and described in Note 6). Interest expense associated with the Company’s outstanding Term Loan Facility was allocated to discontinued operations based on the ratio of the $400 million prepayment to the total outstanding indebtedness under the Term Loan Facility in effect in each respective period.

[4] (4)The effective tax rate on pretax income from discontinued operations was 47.5% for the three months ended March 31, 2017. The 2017 rate differs from the U.S. federal statutory rate of 35% primarily due to state income taxes (net of federal benefit), foreign tax rate differences, and an adjustment relating to the sale of the Gracenote Companies.