Income and Mining Taxes (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Other Information	$17.9 million	16.1	14.3
Income Tax Examination, Penalties and Interest Expense	$ 9.2	$ 6.9	$ 4.1
Minimum [Member]
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	0.5
Maximum [Member]
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	$ 1.0