Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accrued Expenses
Salaries and wages	$ 83,016	$ 90,913
Deferred compensation	3,802	2,992
Pension benefits	3,823	3,796
Other postretirement benefits	1,512	1,506
Other employee benefits	17,071	29,358
Insurance obligations	130,833	127,470
Operating taxes	94,140	92,150
Income taxes	683	4,197
Interest	27,054	27,277
Customer deposits	64,193	61,225
Deferred revenue	16,675	14,064
Other	49,267	52,241
Total	492,069	507,189
Non-Current Liabilities
Salaries and wages	0	0
Deferred compensation	52,021	46,541
Pension benefits	460,551	451,940
Other postretirement benefits	19,023	19,459
Other employee benefits	2,625	5,854
Insurance obligations	268,160	234,336
Operating taxes	0	0
Income taxes	25,267	23,174
Interest	0	0
Customer deposits	4,188	4,569
Deferred revenue	0	0
Other	34,168	31,692
Total	866,003	817,565
Total
Salaries and wages	83,016	90,913
Deferred compensation	55,823	49,533
Pension benefits	464,374	455,736
Other postretirement benefits	20,535	20,965
Other employee benefits	19,696	35,212
Insurance obligations	398,993	361,806
Operating taxes	94,140	92,150
Income taxes	25,950	27,371
Interest	27,054	27,277
Customer deposits	68,381	65,794
Deferred revenue	16,675	14,064
Other	83,435	83,933
Total	$ 1,358,072	$ 1,324,754