Commitments and Contingencies (Details 1) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Mar. 31, 2017
Capital Addition Purchase Commitments [Member]
Long-term Purchase Commitment [Line Items]
Purchase commitments for capital expenditures			$ 20.4
Gold Fields [Member] | Bankruptcy unliquidated, secured and general unsecured [Member]
Loss Contingencies [Line Items]
Bankruptcy Claims, Amount of Claims Filed	$ 1,200.0	$ 2,700.0