Income Taxes - Deferred tax (liabilities) assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Temporary differences [Abstract]
Property, plant and equipment	$ (36,926)	$ (15,962)
Goodwill and other intangible assets	(82,607)	(11,367)
Investments, primarily gains and losses not yet recognized for tax purposes	5,997	6,476
Accrued expenses not deductible until paid	11,329	8,534
Deferred compensation and retiree benefits not deductible until paid	96,463	63,103
Other temporary differences, net	3,410	3,779
Total temporary differences	(2,334)	54,563
Federal and state net operating loss carryforwards	17,005	11,715
Valuation allowance for state deferred tax assets	(1,031)	(912)
Deferred Tax Assets, Net	$ 13,640	$ 65,366