Reclamation and Remediation - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Reclamation and remediation liability
Reclamation and remediation obligations	$ 1,774	$ 1,689	$ 1,579	$ 1,611
Current portion of reclamation and remediation liabilities	55	67
Other current liabilities
Reclamation and remediation liability
Current portion of reclamation and remediation liabilities	62	83
Continuing Operations - Operating
Reclamation and remediation liability
Reclamation and remediation obligations	1,611	1,497
Continuing Operations - Operating | Other current liabilities
Reclamation and remediation liability
Current portion of reclamation and remediation liabilities	36	42
Continuing Operations - Non-Operating
Reclamation and remediation liability
Reclamation and remediation obligations	$ 163	$ 192