XML 86 R65.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Significant Accounting Policies Discussion Textuals (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Nov. 28, 2017
Apr. 01, 2017
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2016
Dec. 31, 2015
Summary of Significant Accounting Policies Textuals            
Period considered to treat short-term, highly liquid investments as cash equivalents     three months or less      
Accounts Receivable Invoicing Terms     Customers are invoiced as coal is shipped or at periodic intervals in accordance with contractual terms      
Recognition of tax benefits from uncertain tax positions     greater than fifty percent likelihood of being realized upon ultimate settlement      
Buildings and improvements [Member]            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     2 to 28      
Machinery and equipment            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     2 to 28      
Leasehold improvements [Member]            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     Shorter of Useful Life or Remaining Life of Lease      
Minimum | Buildings and improvements [Member]            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     2      
Minimum | Machinery and equipment            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     2      
Maximum | Buildings and improvements [Member]            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     28      
Maximum | Machinery and equipment            
Summary of Significant Accounting Policies Textuals            
Estimated useful life     28      
Scenario, Forecast            
Summary of Significant Accounting Policies Textuals            
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income       $ 15.0    
Predecessor            
Summary of Significant Accounting Policies Textuals            
Other-than-temporary impairment losses on equity and cost method investments   $ 0.0       $ 276.5
Restructuring charges for voluntary and involuntary workforce reductions   0.0     $ 15.5 23.5
Asset impairment charges related to long-lived assets   30.5     247.9 1,001.3
Foreign currency remeasurement gain (loss)   10.6     (7.4) (6.4)
Foreign currency translation adjustment   $ 5.5     $ (1.8) $ (34.9)
Successor            
Summary of Significant Accounting Policies Textuals            
Other-than-temporary impairment losses on equity and cost method investments     $ 0.0      
Restructuring charges for voluntary and involuntary workforce reductions $ 3.0   7.6      
Asset impairment charges related to long-lived assets     0.0      
Foreign currency remeasurement gain (loss)     0.7      
Foreign currency translation adjustment     $ 1.4      
Successor | Interest In Middlemount Coal Pty Limited [Member]            
Summary of Significant Accounting Policies Textuals            
Ownership percentage of equity method investment     50.00%