Stock-Based Compensation (Details 2) (USD $)	9 Months Ended
	Sep. 30, 2012
Shares Unvested, January 1, 2012	33,043
Shares Granted	0
Shares Vested	(15,686)
Shares Forfeited	(183)
Shares Unvested, September 30, 2012	17,174
Weighted Average Grant Date Fair Value Unvested, January 1, 2012 (in dollars per share)	$ 49.81
Weighted Average Grant Date Fair Value Granted (in dollars per share)	$ 0
Weighted Average Grant Date Fair Value Vested (in dollars per share)	$ 50.32
Weighted Average Grant Date Fair Value Forfeited (in dollars per share)	$ 46
Weighted Average Grant Date Fair Value Unvested, September 30, 2012 (in dollars per share)	$ 49.45