CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH PROVIDED BY OPERATIONS:
Net income	$ 339,528	$ 208,404
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	198,993	185,241
Deferred income taxes	(5,211)	(12,571)
Provision for pension and other postretirement benefits	9,513	15,776
Share-based compensation expense	17,523	16,370
Loss (gain) on disposals of property and equipment	4,115	(175)
Other postretirement benefit claims paid	(4,856)	(2,358)
Contributions to pension plans	(8,154)	(4,698)
Noncash loss on debt extinguishment	261	0
Contingent payment derivative	(6,382)	0
Changes in current assets and liabilities:
Receivables - trade and other	(139,897)	47,292
Prepaid expenses and other current assets	(3,766)	(10,710)
Accounts payable	11,174	14,681
Accrued income taxes	14,929	3,809
Deferred revenues	(9,443)	4,913
Other current liabilities	(22,802)	(14,769)
Net changes in other noncurrent assets and liabilities	(7,155)	(2,485)
Net cash provided by operations	388,370	448,720
CASH USED IN INVESTING ACTIVITIES:
Capital expenditures	(64,395)	(616,398)
Proceeds from disposals of property and equipment	1,082	2,298
Net cash provided by (used in) investing activities	(63,313)	(614,100)
CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Proceeds from borrowings	0	220,000
Reductions of long-term debt	(47,862)	(170,000)
Dividends paid	0	(25,220)
Net cash provided by (used in) financing activities	(47,862)	24,780
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	277,195	(140,600)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	484,228	339,154
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 761,423	$ 198,554