Stock-Based Compensation Plans (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Summary of the changes in outstanding stock options
Stock Options Outstanding at December 31, 2012 (in shares)			4,083
Stock options, Granted (in shares)	813
Stock options, Exercised (in shares)	(23)
Stock options, Forfeited (in shares)	(176)
Stock Options Outstanding at March 31, 2013 (in shares)	4,697		4,083
Options exercisable at March 31, 2013 (in shares)	2,293
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Outstanding at December 31, 2012 (usd per share)			$ 26.46
Weighted Average Exercise Price / Share, Granted (usd per share)	$ 27.43
Weighted Average Exercise Price / Share, Exercised (usd per share)	$ 20.03
Weighted Average Exercise Price / Share, Forfeited (usd per share)	$ 29.52
Weighted Average Exercise Price, Outstanding at March 31, 2013 (usd per share)	$ 26.54		$ 26.46
Options exercisable, Weighted Average Exercise Price (usd per share)	$ 26.22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Roll Forward]
Weighted Average Remaining Contractual Term, Outstanding at December 31, 2012	7 years 3 months 18 days	6 years 4 months 26 days
Weighted Average Remaining Contractual Term, Options Granted	10 years
Weighted Average Remaining Contractual Term, Options Exercised	3 years 4 months 24 days
Weighted Average Remaining Contractual Term, Options Forfeited	1 month 6 days
Weighted Average Remaining Contractual Term, Outstanding at March 31, 2013	7 years 3 months 18 days	6 years 4 months 26 days
Weighed average remaining contractual term, Options exercisable	5 years 2 months 12 days