Segment Information (Reconciliation of Segment Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reconciliation of segment income to net income
Segment income				$ (19.6)
Other (income) expense
Change in fair value of common stock purchase warrants	0	1.9	0	1.8
General and administrative	5.5	6.4	12.6	14.1
Exploration	0.5	0.6	0.6	1.4
Interest expense (income), net	(0.1)	(1.5)	(0.2)	(3.0)
(Gain) loss on foreign exchange	(34.8)	(7.9)	(54.2)	(1.3)
Other	0.2	0.1	0.2	0.4
(Loss) income before income and mining taxes	(17.2)	(25.6)	(19.5)	(36.6)
Income and mining tax expense (benefit)	2.0	(10.8)	(1.2)	(22.9)
Net loss	(19.2)	(14.8)	(18.3)	(13.7)
Unallocated amount to segment
Reconciliation of segment income to net income
Segment income	18.7		37.3
Other (income) expense
Change in fair value of common stock purchase warrants	0	(1.9)	0	(1.8)
General and administrative	5.5	6.4	12.6	14.1
Exploration	0.5	0.6	0.6	1.4
Interest expense (income), net	(0.2)	1.3	(0.3)	2.6
(Gain) loss on foreign exchange	29.9	2.3	43.2	0.2
Corporate depreciation	0.4	0.3	0.9	0.9
Other	(0.2)	(0.1)	(0.2)	(0.4)
(Loss) income before income and mining taxes	(17.2)	(25.6)	(19.5)	(36.6)
Income and mining tax expense (benefit)	2.0	(10.8)	(1.2)	(22.9)
Net loss	$ (19.2)	$ (14.8)	$ (18.3)	$ (13.7)