Capital Stock and Stock Options (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
[RestrictedStockMember]
Stock based compensation plans
Total unrecognized compensation cost	$ 8.5
Weighted-average vesting period over which unrecognized compensation is expected to be recognized	2 years 3 months 18 days
[EmployeeStockOptionMember]
Stock based compensation plans
Exercised (in shares)	30,150
Number of shares withheld and subsequently canceled and retired	19,959