Employee Benefit Plans - Pension Expense From Continuing Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Union-administered plans
Amortization of:
Postretirement benefit income	$ 9,326	$ 15,553	$ 9,597
Pension Plans
Pension expense from continuing operations
Service cost	12,108	12,345
Interest cost	78,234	86,431
Pension settlement expense	0	71,299
Amortization of:
Postretirement benefit income	29,892	56,833	61,215
Pension Plans | Company-administered plans:
Pension expense from continuing operations
Service cost	12,108	12,345	12,977
Interest cost	78,234	86,431	94,476
Expected return on plan assets	(101,980)	(91,062)	(90,588)
Pension settlement expense	3,061	0	0
Amortization of:
Net actuarial gain	28,593	32,987	31,777
Prior service cost	550	579	2,976
Postretirement benefit income	20,566	41,280	51,618
Pension Plans | Union-administered plans
Amortization of:
Postretirement benefit income	9,326	15,553	9,597
Pension Plans | United States | Company-administered plans:
Amortization of:
Postretirement benefit income	28,043	43,717	53,319
Pension Plans | Domestic Plan | Company-administered plans:
Amortization of:
Postretirement benefit income	$ (7,477)	$ (2,437)	$ (1,701)