CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CASH PROVIDED BY OPERATIONS:
Net income	$ 122,799	$ 123,669
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	98,852	90,564
Deferred income taxes	(12,568)	(7,541)
Provision for pension and other postretirement benefits	4,756	7,844
Share-based compensation expense	8,203	5,190
Loss (gain) on disposals of property, plant and equipment	2,177	(513)
Other postretirement benefit claims paid	(3,018)	(1,115)
Contributions to pension plans	(3,135)	(375)
Noncash loss on debt extinguishment	86	0
Changes in current assets and liabilities:
Receivables - trade and other	(16,390)	42,053
Prepaid expenses and other current assets	6,793	4,350
Accounts payable	(17,215)	6,894
Accrued income taxes	5,247	12,300
Deferred revenues	(2,539)	1,163
Other current liabilities	(30,914)	(47,075)
Net changes in other noncurrent assets and liabilities	(3,083)	7,358
Net cash provided by operations	160,051	244,766
CASH USED IN INVESTING ACTIVITIES:
Capital expenditures	(32,908)	(514,265)
Proceeds from disposals of property, plant and equipment	299	1,680
Net cash used in investing activities	(32,609)	(512,585)
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Reductions of long-term debt	(16,470)	0
Dividends paid	0	(12,562)
Excess tax benefit from share-based compensation	0	(1,981)
Net cash used in financing activities	(16,470)	(14,543)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	110,972	(282,362)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	484,228	339,154
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 595,200	$ 56,792