Capital Stock - Options outstanding and exercisable (Details) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 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)	$ 10
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 2016
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 3 months 15 days
Options on Shares Outstanding	2,055,210
Options on Shares Exercisable	2,055,210
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 9.07
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 9.07
Options Outstanding, Aggregate Intrinsic Value	$ 14.9
Options Exercisable, Aggregate Intrinsic Value	14.9
Stock Options | Options Granted, Range One [Member]
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	2 months 5 days
Options on Shares Outstanding	3,794
Options on Shares Exercisable	3,794
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 9.78
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 9.78
Options Outstanding, Aggregate Intrinsic Value	0
Options Exercisable, Aggregate Intrinsic Value	0
Stock Options | 2004 – expire in 2014
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	6 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	1 year 7 months 27 days
Options on Shares Outstanding	47,737
Options on Shares Exercisable	47,737
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 10.03
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 10.03
Options Outstanding, Aggregate Intrinsic Value	0.3
Options Exercisable, Aggregate Intrinsic Value	0.3
Stock Options | 2006 – expire in 2016
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	5 months 2 days
Options on Shares Outstanding	349,497
Options on Shares Exercisable	349,497
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 10.27
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 10.27
Options Outstanding, Aggregate Intrinsic Value	2.1
Options Exercisable, Aggregate Intrinsic Value	2.1
Stock Options | 2007 – expire in 2015
Information about options outstanding and options exercisable by year of grant
Average Remaining Term	1 year 6 months 0 days
Options on Shares Outstanding	1,610,994
Options on Shares Exercisable	1,610,994
Options Outstanding, Weighted Average Exercise Price (USD per share)	$ 8.73
Options Exercisable, Weighted Average Exercise Price (USD per share)	$ 8.73
Options Outstanding, Aggregate Intrinsic Value	12.2
Options Exercisable, Aggregate Intrinsic Value	$ 12.2