Fresh Start Accounting (Fresh Start) (Details) - USD ($)	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Feb. 03, 2021	Feb. 02, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 258,024,000				$ 172,768,000	$ 188,006,000	$ 207,781,000			$ 272,624,000
Restricted cash-current					16,751,000
Accounts receivable, net					153,529,000
Income taxes receivable					8,976,000
Prepaid expenses	26,881,000				31,630,000	31,793,000
Inventory and Other Current Assets	71,684,000				101,140,000	77,027,000
Assets held for sale					220,359,000
Total current assets	644,206,000				705,153,000	715,508,000
Property, plant and equipment, net	403,473,000				540,850,000	408,107,000
Operating lease right-of-use assets					33,918,000
Goodwill	0				138,900,000	138,677,000
Notes receivable					72,484,000
Restricted Cash and Cash Equivalents, Noncurrent	79,560,000				80,179,000	80,178,000	80,175,000			2,764,000
Finite-Lived Intangible Assets, Net	5,882,000				24,220,000	4,996,000
Total assets	1,255,783,000				1,456,804,000	1,501,079,000
Current liabilities:
Accounts payable	56,500,000				51,116,000	50,330,000
Accrued expenses	109,054,000				137,216,000	114,777,000
Liabilities held for sale	23,241,000				37,264,000	46,376,000
Total current liabilities	188,795,000				225,596,000	211,483,000
Decommissioning liabilities	173,132,000				169,515,000	134,436,000
Operating lease liabilities	20,608,000				23,555,000	29,464,000
Deferred income taxes	32,396,000				59,522,000	5,288,000
Other long-term liabilities	70,355,000				75,930,000	123,261,000
Total non-current liabilities	296,491,000				328,522,000	292,449,000
Liabilities subject to compromise	0				1,572,772,000	1,335,794,000
Total liabilities	485,286,000				554,118,000	1,839,726,000
Stockholders’ equity (deficit):
Common Stock $0.001 par value	0				200,000	16,000
Treasury Stock at Cost	0					4,290,000
Additional paid-in capital					902,486,000
Accumulated other comprehensive loss, net	0					(67,947,000)
Accumulated deficit	(132,830,000)					(3,023,315,000)
Total stockholders’ equity (deficit)	770,497,000	$ 815,142,000	$ 866,056,000	$ 902,686,000	902,686,000	(338,647,000)	$ (249,736,000)	$ (95,127,000)	$ (32,110,000)	$ 49,573,000
Total liabilities and stockholders’ equity (deficit)	1,255,783,000				1,456,804,000	$ 1,501,079,000
Reorganization Adjustments [Member]
Current assets:
Cash and cash equivalents					(21,903,000)
Restricted cash-current					16,751,000
Accounts receivable, net					11,000
Total current assets					(5,141,000)
Finite-Lived Intangible Assets, Net					(10,080,000)
Total assets					(15,221,000)
Current liabilities:
Accounts payable					(700,000)
Accrued expenses					9,042,000
Liabilities held for sale					1,614,000
Total current liabilities					9,956,000
Deferred income taxes					3,100,000
Total non-current liabilities					3,100,000
Liabilities subject to compromise					(1,572,772,000)
Total liabilities					(1,559,716,000)
Stockholders’ equity (deficit):
Common Stock $0.001 par value					200,000
common stock $0.001 par value					(16,000)
Additional paid-in capital					(2,757,824,000)
Treasury Stock at Cost					4,290,000
Additional paid-in capital					902,486,000
Accumulated deficit					3,395,359,000
Total stockholders’ equity (deficit)					1,544,495,000
Total liabilities and stockholders’ equity (deficit)					(15,221,000)
Reorganization, Chapter 11, Fresh-Start Adjustment [Member]
Current assets:
Restricted cash-current					16,751,000
Income taxes receivable					(170,000)
Inventory and Other Current Assets					11,067,000
Assets held for sale					(20,402,000)
Total current assets					(9,505,000)
Property, plant and equipment, net					139,587,000
Operating lease right-of-use assets					1,430,000
Goodwill					(138,934,000)
Finite-Lived Intangible Assets, Net					(17,964,000)
Total assets					(25,386,000)
Current liabilities:
Accrued expenses					1,406,000
Liabilities held for sale					(3,992,000)
Total current liabilities					(2,586,000)
Decommissioning liabilities					34,581,000
Operating lease liabilities					(29,000)
Deferred income taxes					51,569,000
Other long-term liabilities					(45,826,000)
Total non-current liabilities					40,295,000
Total liabilities					37,709,000
Stockholders’ equity (deficit):
Accumulated other comprehensive loss, net					67,532,000
Accumulated deficit					(130,627,000)
Total stockholders’ equity (deficit)					(63,095,000)
Total liabilities and stockholders’ equity (deficit)					(25,386,000)
Reorganization, Chapter 11, Predecessor, before Adjustment [Member]
Current assets:
Cash and cash equivalents					194,671,000
Accounts receivable, net					153,518,000
Income taxes receivable					9,146,000
Prepaid expenses					31,630,000
Inventory and Other Current Assets					90,073,000
Assets held for sale					240,761,000
Total current assets					719,799,000
Property, plant and equipment, net					401,263,000
Operating lease right-of-use assets					32,488,000
Goodwill					138,934,000
Notes receivable					72,484,000
Restricted Cash and Cash Equivalents, Noncurrent					80,179,000
Finite-Lived Intangible Assets, Net					52,264,000
Total assets	1,456,800,000				1,497,411,000
Current liabilities:
Accounts payable					51,816,000
Accrued expenses					126,768,000
Liabilities held for sale					39,642,000
Total current liabilities					218,226,000
Decommissioning liabilities					134,934,000
Operating lease liabilities					23,584,000
Deferred income taxes					4,853,000
Other long-term liabilities					121,756,000
Total non-current liabilities					285,127,000
Liabilities subject to compromise					1,572,772,000
Total liabilities	$ 2,076,100,000				2,076,125,000
Stockholders’ equity (deficit):
Common Stock $0.001 par value					16,000
Treasury Stock at Cost					(4,290,000)
Additional paid-in capital					2,757,824,000
Accumulated other comprehensive loss, net					(67,532,000)
Accumulated deficit					(3,264,732,000)
Total stockholders’ equity (deficit)					(578,714,000)
Total liabilities and stockholders’ equity (deficit)					$ 1,497,411,000