Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Financing activities
Net loss resulting from early retirement of debt and debt restructuring	$ (2,100,000)	$ (2,200,000)
Cash and cash equivalents, beginning of period	305,372,000
Cash and cash equivalents, end of period	333,548,000
Successor
Operating activities
Net income (loss)	88,828,000
Adjustments to reconcile to cash provided by operating activities:
Depreciation, depletion and amortization	62,622,000
Accretion on asset retirement obligations	15,246,000
Amortization of sales contracts, net	29,042,000
Prepaid royalties expensed	2,288,000
Deferred income taxes	5,996,000
Employee stock-based compensation expense	4,942,000
Gains on disposals and divestitures, net	(2,005,000)
Asset impairment and non-cash mine closure costs	0
Net loss resulting from early retirement of debt and debt restructuring	2,061,000
Non-cash bankruptcy reorganization items	0
Amortization relating to financing activities	1,565,000
Changes in:
Receivables	(3,864,000)
Inventories	(23,594,000)
Accounts payable, accrued expenses and other current liabilities	(89,000)
Income taxes, net	(3,796,000)
Other	21,557,000
Cash provided by (used in) operating activities	200,799,000
Investing activities
Capital expenditures	(16,922,000)
Minimum royalty payments	(4,211,000)
Proceeds from (consideration paid for) disposals and divestitures	4,186,000
Purchases of short term investments	(157,364,000)
Proceeds from sales of short term investments	85,035,000
Investments in and advances to affiliates, net	(8,934,000)
Withdrawals (deposits) of restricted cash	29,295,000
Cash used in investing activities	(68,915,000)
Financing activities
Proceeds from issuance of term loan due 2024	298,500,000
Payments to extinguish term loan due 2021	(325,684,000)
Payments on term loan due 2024	(750,000)
Net payments on other debt	(5,207,000)
Debt financing costs	(8,900,000)
Net loss resulting from early retirement of debt and debt restructuring	(2,061,000)
Dividends paid	(8,563,000)
Purchases of treasury stock	(51,043,000)
Cash used in financing activities	(103,708,000)
Increase (decrease) in cash and cash equivalents	28,176,000
Cash and cash equivalents, beginning of period	305,372,000
Cash and cash equivalents, end of period	$ 333,548,000
Predecessor
Operating activities
Net income (loss)		(382,589,000)
Adjustments to reconcile to cash provided by operating activities:
Depreciation, depletion and amortization		122,158,000
Accretion on asset retirement obligations		16,356,000
Amortization of sales contracts, net		(832,000)
Prepaid royalties expensed		1,770,000
Deferred income taxes		(418,000)
Employee stock-based compensation expense		1,435,000
Gains on disposals and divestitures, net		(6,269,000)
Asset impairment and non-cash mine closure costs		119,194,000
Net loss resulting from early retirement of debt and debt restructuring		2,213,000
Non-cash bankruptcy reorganization items		(14,892,000)
Amortization relating to financing activities		7,657,000
Changes in:
Receivables		(7,776,000)
Inventories		21,152,000
Accounts payable, accrued expenses and other current liabilities		84,160,000
Income taxes, net		(937,000)
Other		(22,634,000)
Cash provided by (used in) operating activities		(60,252,000)
Investing activities
Capital expenditures		(74,137,000)
Minimum royalty payments		(217,000)
Proceeds from (consideration paid for) disposals and divestitures		(3,303,000)
Purchases of short term investments		(98,750,000)
Proceeds from sales of short term investments		94,589,000
Investments in and advances to affiliates, net		(2,890,000)
Withdrawals (deposits) of restricted cash		(4,695,000)
Cash used in investing activities		(89,403,000)
Financing activities
Payments on term loan due 2024		0
Net payments on other debt		(10,293,000)
Debt financing costs		(18,806,000)
Net loss resulting from early retirement of debt and debt restructuring		(2,213,000)
Dividends paid		0
Purchases of treasury stock		0
Cash used in financing activities		(31,312,000)
Increase (decrease) in cash and cash equivalents		(180,967,000)
Cash and cash equivalents, beginning of period		450,781,000
Cash and cash equivalents, end of period		$ 269,814,000