Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income, balance at beginning of the period	$ (81,782)	$ (71,016)
Other comprehensive (loss) income before reclassifications	20,798	(10,590)
Amounts reclassified from AOCI	12,923	(176)
Accumulated other comprehensive (loss) income, balance at the end of the period	(48,061)	(81,782)	$ (71,016)
Cumulative translation adjustments	33,721	(10,766)	(24,475)
Pension and other Post-Retirement Benefit Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income, balance at beginning of the period	(64,883)	(57,391)
Other comprehensive (loss) income before reclassifications	19,231	(7,316)
Amounts reclassified from AOCI	(160)	(176)
Accumulated other comprehensive (loss) income, balance at the end of the period	(45,812)	(64,883)	(57,391)
Marketable Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income, balance at beginning of the period	3,075	2,139
Other comprehensive (loss) income before reclassifications	(95)	936
Amounts reclassified from AOCI	(2,980)	0
Accumulated other comprehensive (loss) income, balance at the end of the period	0	3,075	2,139
Cash Flow Hedging Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income, balance at beginning of the period	0	0
Other comprehensive (loss) income before reclassifications	(3,591)	0
Amounts reclassified from AOCI	3,298	0
Accumulated other comprehensive (loss) income, balance at the end of the period	(293)	0	0
Foreign Currency Translation Adjustments (1)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive (loss) income, balance at beginning of the period	(19,974)	(15,764)
Other comprehensive (loss) income before reclassifications	5,253	(4,210)
Amounts reclassified from AOCI	12,765	0
Accumulated other comprehensive (loss) income, balance at the end of the period	(1,956)	$ (19,974)	$ (15,764)
Foreign Currency Translation Adjustments (1) | CareerBuilder, LLC
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative translation adjustments	4,000
Foreign Currency Translation Adjustments (1) | Gracenote Companies
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative translation adjustments	$ 9,000