Income taxes - Summary of Activity Related to Unrecognized Tax Benefits, Excluding Federal Tax Benefit of State Tax Deductions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in unrecognized tax benefits
Balance at beginning of year	$ 17,300	$ 19,491	$ 58,886
Additions based on tax positions related to the current year	156	213	6,095
Additions for tax positions of prior years	11	162	853
Reductions for tax positions of prior years	(636)	(1,214)	(24,858)
Settlements	(852)	0	0
Reductions for transfers to Gannett Co., Inc.	0	0	(18,804)
Reductions due to lapse of statutes of limitations	(936)	(1,352)	(2,681)
Balance at end of year	$ 15,043	$ 17,300	$ 19,491