Income Taxes - Deferred tax (liabilities) assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Temporary differences [Abstract]
Property and equipment	$ (14,545)	$ (14,493)
Goodwill and other intangible assets	(81,721)	(52,532)
Investments, primarily gains and losses not yet recognized for tax purposes	3,067	2,792
Accrued expenses not deductible until paid	8,792	7,136
Deferred compensation and retiree benefits not deductible until paid	56,902	61,070
Other temporary differences, net	3,416	3,267
Total temporary differences	(24,089)	7,240
Federal and state net operating loss carryforwards	12,800	15,455
Valuation allowance for state deferred tax assets	(5,101)	(2,619)
Net deferred tax liability	(16,390)
Net deferred tax asset	$ 9,000	$ 20,076