Capital Stock - Options outstanding and exercisable (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Information about options outstanding and options exercisable by year of grant
Range of Exercise Prices, Lower Range Limit (USD per share)	$ 7
Range of Exercise Prices, Upper Range Limit (USD per share)	$ 11
Options Granted, Range One [Member]
Information about options outstanding and options exercisable by year of grant
Range of Exercise Prices, Lower Range Limit (USD per share)	$ 10
Range of Exercise Prices, Upper Range Limit (USD per share)	$ 11
2004 – expire in 2014
Information about options outstanding and options exercisable by year of grant
Range of Exercise Prices, Lower Range Limit (USD per share)	$ 10
Range of Exercise Prices, Upper Range Limit (USD per share)	$ 11
2005 – expire in 2015
Information about options outstanding and options exercisable by year of grant
Range of Exercise Prices, Lower Range Limit (USD per share)	$ 10
Range of Exercise Prices, Upper Range Limit (USD per share)	$ 11
2006 – expire in 2014
Information about options outstanding and options exercisable by year of grant
Range of Exercise Prices, Lower Range Limit (USD per share)	$ 9
Range of Exercise Prices, Upper Range Limit (USD per share)	$ 10
2007 – expire in 2015
Information about options outstanding and options exercisable by year of grant
Range of Exercise Prices, Lower Range Limit (USD per share)	$ 7
Range of Exercise Prices, Upper Range Limit (USD per share)	$ 10
Stock Options
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	1 year 7 months 14 days
Options on Shares Outstanding	2,695,905
Options on Shares Exercisable	2,695,905
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 9.28
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 9.28
Options Outstanding, Aggregate Intrinsic Value	$ 22.8
Options Exercisable, Aggregate Intrinsic Value	22.8
Stock Options | Options Granted, Range One [Member]
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	5 months 15 days
Options on Shares Outstanding	15,373
Options on Shares Exercisable	15,373
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 10.40
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 10.40
Options Outstanding, Aggregate Intrinsic Value	0.1
Options Exercisable, Aggregate Intrinsic Value	0.1
Stock Options | 2004 – expire in 2014
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	1 year 0 months 14 days
Options on Shares Outstanding	43,188
Options on Shares Exercisable	43,188
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 10.90
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 10.90
Options Outstanding, Aggregate Intrinsic Value	0.3
Options Exercisable, Aggregate Intrinsic Value	0.3
Stock Options | 2005 – expire in 2015
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	2 months 7 days
Options on Shares Outstanding	63,214
Options on Shares Exercisable	63,214
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 10.05
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 10.05
Options Outstanding, Aggregate Intrinsic Value	0.5
Options Exercisable, Aggregate Intrinsic Value	0.5
Stock Options | 2006 – expire in 2014
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	10 months 27 days
Options on Shares Outstanding	752,731
Options on Shares Exercisable	752,731
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 10.34
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 10.34
Options Outstanding, Aggregate Intrinsic Value	5.6
Options Exercisable, Aggregate Intrinsic Value	5.6
Stock Options | 2007 – expire in 2015
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	1 year 11 months 28 days
Options on Shares Outstanding	1,821,399
Options on Shares Exercisable	1,821,399
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 8.77
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 8.77
Options Outstanding, Aggregate Intrinsic Value	16.3
Options Exercisable, Aggregate Intrinsic Value	$ 16.3