Income taxes - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Tax Cuts and Jobs Act, reduction of tax expense		$ 5,400
Capital loss carryforwards	$ 452,900
Loss carryforwards	120,695	132,214
Deferred tax assets valuation allowance	125,894	136,418
Increase (decrease) in valuation allowance	(10,500)
Unrecognized tax benefits that, if recognized, would impact effective tax rate	10,600	10,700
Recognized interest and the release of penalty reserves	200	300	$ 700
Accrued interest and penalties payable related to unrecognized tax benefits	1,400	$ 1,600
Estimated decrease in gross unrecognized tax positions within the next 12 months, maximum	3,900
State
Income Taxes [Line Items]
Tax credit carryforward	18,600
Loss carryforwards	$ 400
Tax years subject to examination	Tax years before 2015 remain subject to examination by certain states due to ongoing audits.
Federal
Income Taxes [Line Items]
Tax years subject to examination	The 2015 through 2018 tax years remain subject to examination by the Internal Revenue Service and state authorities.
Tax Year 2020
Income Taxes [Line Items]
Capital loss carryforwards subject to expiration	$ 351,800
Capital Loss Deferred Tax Assets
Income Taxes [Line Items]
Increase (decrease) in valuation allowance	(14,400)
CareerBuilder, LLC Deferred Tax Assets
Income Taxes [Line Items]
Increase (decrease) in valuation allowance	$ 3,900