Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 154,800	$ 213,600	$ 245,300
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	152,200	134,000	116,900
Deferred and noncurrent income tax charges (benefits)	23,700	37,900	(50,400)
Loss on early debt extinguishment	14,800	0	0
Accretion of asset retirement obligations	2,100	2,000	1,800
Pretax (gains) losses from sale of assets	(100)	1,100	3,900
Net decrease (increase) in noncash operating working capital	(48,700)	2,300	(36,900)
Other operating activities - net	14,500	7,800	3,000
Net cash provided by operating activities	313,300	398,700	283,600
Investing Activities
Property additions	(204,800)	(204,300)	(258,300)
Proceeds from sale of assets	2,500	1,200	900
Other investing activities - net	(800)	(6,000)	(4,700)
Net cash required by investing activities	(203,100)	(209,100)	(262,100)
Financing Activities
Purchase of treasury stock	(165,800)	(144,400)	(206,000)
Repayments of debt	(573,400)	(21,300)	(131,400)
Borrowings of debt	743,800	0	338,800
Early debt extinguishment costs	(10,400)	0	0
Debt issuance costs	(4,100)	0	(1,100)
Amounts related to share-based compensation	(4,500)	(9,400)	(5,600)
Net cash required by financing activities	(14,400)	(175,100)	(5,300)
Net change in cash, cash equivalents, and restricted cash	95,800	14,500	16,200
Cash, cash equivalents, and restricted cash at January 1	184,500	170,000	153,800
Cash, cash equivalents, and restricted cash at December 31	280,300	184,500	170,000
Reconciliation of Cash, Cash Equivalents and Restricted Cash
Cash, cash equivalents, and restricted cash	$ 280,300	$ 170,000	$ 170,000