Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Expenses
Salaries and wages	$ 133,733	$ 90,913
Deferred compensation	4,269	2,992
Pension benefits	3,863	3,796
Other postretirement benefits	1,481	1,506
Other employee benefits	28,636	29,358
Insurance obligations	130,848	127,470
Operating taxes	95,848	92,150
Income taxes	8,550	4,197
Interest	30,003	27,277
Deposits, mainly from customers	69,903	61,225
Deferred revenue	14,004	14,064
Restructuring liabilities	13,074	7,278
Other	53,194	44,963
Total	587,406	507,189
Non-Current Liabilities
Salaries and wages	0	0
Deferred compensation	58,411	46,541
Pension benefits	412,417	451,940
Other postretirement benefits	19,760	19,459
Other employee benefits	3,279	5,854
Insurance obligations	242,473	234,336
Operating taxes	0	0
Income taxes	24,160	23,174
Interest	0	0
Deposits, mainly from customers	3,638	4,569
Deferred revenue	0	0
Restructuring liabilities	0	0
Other	47,951	31,692
Total	812,089	817,565
Total
Salaries and wages	133,733	90,913
Deferred compensation	62,680	49,533
Pension benefits	416,280	455,736
Other postretirement benefits	21,241	20,965
Other employee benefits	31,915	35,212
Insurance obligations	373,321	361,806
Operating taxes	95,848	92,150
Income taxes	32,710	27,371
Interest	30,003	27,277
Deposits, mainly from customers	73,541	65,794
Deferred revenue	14,004	14,064
Restructuring liabilities	13,074	7,278
Other	101,145	76,655
Total	$ 1,399,495	$ 1,324,754