Share-Based Compensation Plans (Details 4) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Summary of employee stock purchase plan
Outstanding Ending Balance, Shares	3,148
Exercisable, Shares	2,032
Outstanding weighted average exercise price, Ending Balance	$ 46.36
Exercisable, weighted average exercise price	$ 45.76
Outstanding, weighted average remaining contractual term	3 years 7 months 2 days
Employee Stock Purchase Plan [Member]
Summary of employee stock purchase plan
Outstanding Beginning Balance, Shares	0
Granted, Shares	268
Exercised, Shares	(268)
Forfeited or expired, Shares	0
Outstanding Ending Balance, Shares	0
Exercisable, Shares	0
Outstanding, weighted average exercise price, Beginning Balance	$ 0.00
Granted, weighted average exercise price	$ 33.72
Exercised, weighted average exercise price	$ 33.72
Forfeited or expired, weighted average exercise price	$ 0.00
Outstanding weighted average exercise price, Ending Balance	$ 0.00
Exercisable, weighted average exercise price	$ 0.00
Outstanding, weighted average remaining contractual term	0 years
Exercisable, weighted average remaining contractual term	0 years
Exercisable, Aggregate Intrinsic Value of In-The-Money Options	$ 0