Supplemental Equity Information - Reclassifications out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	$ 2,473	$ 24,225	$ 11,325	$ 38,370
Income tax effect	(622)	(850)	(2,880)	(2,543)
Total reclassifications, net of tax	1,851	23,375	8,445	35,827
Amortization of prior service (credit) cost
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	(101)	16	(302)	48
Amortization of actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	1,376	2,185	4,129	6,555
Reclassification of CareerBuilder foreign currency translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	0	22,024	0	22,024
Total reclassifications, net of tax	0	22,024	0	22,024
Reclassification of available for sale investment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	0	0	0	9,743
Pension payment timing related charges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, before tax	$ 1,198	$ 0	$ 7,498	$ 0