Stock-based Compensation (Details 4) (Stock Appreciation Rights (Sars) [Member], USD $)	12 Months Ended
	Dec. 31, 2012
Stock Appreciation Rights (Sars) [Member]
Balance, beginning (in shares)	365,845
Granted, (in shares)	92,352
Forfeited, (in shares)	(1,005)
Exercised, (in shares)	(105,311)
Balance, ending (in shares)	351,881
Exercisable, (in shares)	190,587
Outstanding, weighted average exercise price (in dollars per share)	$ 24.43
Granted, weighted average exercise price (in dollars per share)	$ 33.56
Forfeited, Weighted Average Exercise Price (in dollars per share)	$ 33.56
Exercised, weighted average exercise price (in dollars per share)	$ 21.87
Outstanding, weighted average exercise price (in dollars per share)	$ 27.52
Exercisable, weighted average exercise price (in dollars per share)	$ 23.98