Supplemental Guarantor Information (Condensed Consolidating Statements of Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net cash provided by (used in) operating activities	$ 68,830	$ 39,415
Cash flows from investing activities:
Payments for capital expenditures	(79,136)	(119,841)
Proceeds from sales of assets	84,557	23,297
Net cash provided by (used in) investing activities	5,421	(96,544)
Cash flows from financing activities:
Other	(1,026)	(3,900)
Net cash provided by (used in) financing activities	(1,026)	(3,900)
Effect of exchange rate changes on cash	(102)	(1,311)
Net change in cash, cash equivalents, and restricted cash	73,123	(62,340)
Cash, cash equivalents, and restricted cash at beginning of period	163,748	192,483
Cash, cash equivalents, and restricted cash at end of period	236,871	130,143
Eliminations [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities		(11,269)
Cash flows from financing activities:
Intercompany dividends		11,269
Net cash provided by (used in) financing activities		11,269
Parent [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	10,232	12,342
Cash flows from financing activities:
Changes in notes with affiliated companies, net	(9,206)	(8,834)
Other	(1,026)	(3,508)
Net cash provided by (used in) financing activities	(10,232)	(12,342)
Issuer [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	(246,583)	(91,600)
Cash flows from investing activities:
Payments for capital expenditures	(3,290)	(549)
Net cash provided by (used in) investing activities	(3,290)	(549)
Cash flows from financing activities:
Changes in notes with affiliated companies, net	319,285	34,815
Other		(392)
Net cash provided by (used in) financing activities	319,285	34,423
Net change in cash, cash equivalents, and restricted cash	69,412	(57,726)
Cash, cash equivalents, and restricted cash at beginning of period	102,224	126,533
Cash, cash equivalents, and restricted cash at end of period	171,636	68,807
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	288,600	131,729
Cash flows from investing activities:
Payments for capital expenditures	(72,981)	(114,360)
Proceeds from sales of assets	84,557	10,150
Net cash provided by (used in) investing activities	11,576	(104,210)
Cash flows from financing activities:
Changes in notes with affiliated companies, net	(302,459)	(35,613)
Net cash provided by (used in) financing activities	(302,459)	(35,613)
Net change in cash, cash equivalents, and restricted cash	(2,283)	(8,094)
Cash, cash equivalents, and restricted cash at beginning of period	6,360	20,923
Cash, cash equivalents, and restricted cash at end of period	4,077	12,829
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by (used in) operating activities	16,581	(1,787)
Cash flows from investing activities:
Payments for capital expenditures	(2,865)	(4,932)
Proceeds from sales of assets		13,147
Net cash provided by (used in) investing activities	(2,865)	8,215
Cash flows from financing activities:
Intercompany dividends		(11,269)
Changes in notes with affiliated companies, net	(7,620)	9,632
Net cash provided by (used in) financing activities	(7,620)	(1,637)
Effect of exchange rate changes on cash	(102)	(1,311)
Net change in cash, cash equivalents, and restricted cash	5,994	3,480
Cash, cash equivalents, and restricted cash at beginning of period	55,164	45,027
Cash, cash equivalents, and restricted cash at end of period	$ 61,158	$ 48,507