Segment Information (Reconciliation of Segment Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reconciliation of segment income to net income
Segment income				$ (33.3)
Other (income) expense
Goodwill impairment	0	47.0	0	47.0
Change in fair value of common stock purchase warrants	0	0	0	(1.8)
General and administrative	5.1	7.0	17.7	22.1
Start-up costs	10.2	0.2	10.3	5.3
Exploration	0.7	0.5	1.3	1.9
Interest expense (income), net	0.7	1.5	0.9	4.5
(Gain) loss on foreign exchange	(24.2)	(21.3)	30.0	(20.0)
Other	0.2	0.1	0	(0.3)
(Loss) income before income and mining taxes	18.0	(64.2)	(1.5)	(100.8)
Income and mining tax expense (benefit)	4.2	(16.0)	3.0	(38.9)
Net income (loss)	13.8	(48.2)	(4.5)	(61.9)
Unallocated amount to segment
Reconciliation of segment income to net income
Segment income	14.6	(19.8)	52.0
Other (income) expense
Goodwill impairment	0	47.0	0	47.0
Change in fair value of common stock purchase warrants	0	0	0	(1.8)
General and administrative	5.1	7.0	17.7	22.1
Exploration	0.7	0.5	1.3	1.9
Interest expense (income), net	0.3	1.0	0	3.6
(Gain) loss on foreign exchange	(20.4)	(12.0)	22.8	(11.8)
Corporate depreciation	0.5	0.6	1.4	1.5
Other	0.2	0.1	0	(0.3)
(Loss) income before income and mining taxes	18.0	(64.2)	(1.5)	(100.8)
Income and mining tax expense (benefit)	4.2	(16.0)	3.0	(38.9)
Net income (loss)	$ 13.8	$ (48.2)	$ (4.5)	$ (61.9)