XML 117 R104.htm IDEA: XBRL DOCUMENT v3.7.0.1
Leases (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Future minimum lease and royalty payments      
Capital Leases, 2017 $ 7.3    
Capital Leases, 2018 8.9    
Capital Leases, 2019 0.5    
Capital Leases, 2020 0.5    
Capital Leases, 2021 0.5    
Capital Leases, 2022 and Thereafter 9.6    
Capital Leases, Total minimum lease payments 27.3    
Capital Leases, Less interest 7.6    
Capital Leases, Present value of minimum capital lease payments 19.7    
Operating Leases, 2017 148.7    
Operating Leases, 2018 100.4    
Operating Leases, 2019 60.2    
Operating Leases, 2020 26.4    
Operating Leases, 2021 10.6    
Operating Leases, 2022 and thereafter 26.6    
Operating Leases, Total minimum lease payments 372.9    
Coal Lease and Royalty Obligation, 2017 6.1    
Coal Lease and Royalty Obligation, 2018 5.7    
Coal Lease and Royalty Obligation, 2019 5.2    
Coal Lease and Royalty Obligation, 2020 4.9    
Coal Lease and Royalty Obligation, 2021 5.3    
Coal Lease and Royalty Obligation, 2022 and Thereafter 26.6    
Coal Lease and Royalty Obligation, Total minimum lease payments 53.8    
Leases (Textuals)      
Rental expense under operating leases 264.7 $ 290.1 $ 306.0
Contingent lease expense 0.0 0.0 0.0
Property, plant, equipment and mine development assets, gross value under capital leases 77.9 77.5  
Accumulated depreciation of property, plant, equipment and mine development assets under capital leases 48.6 32.2  
Total royalty expenses on coal reserve leases $ 389.7 $ 444.5 $ 507.8
Initial lease term for federal leases ten years    
Minimum annual production on federal leases 1.00%    
Monthly royalty percentage on federal leases for coal sales using surface mining methods 12.50%    
Monthly royalty percentage on federal leases for coal production using underground mining methods 8.00%    
Period to redetermine royalty rates on leased coal reserves in Arizona every ten years    
Company's lease obligations secured by outstanding surety bonds $ 94.0