Share-based Payment Arrangements (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Grant date fair value per share	$ 2.52	$ 3.62
Expected term (in years)	5 years 9 months 18 days	6 years
Expected volatility	30.90%	35.00%
Risk free interest rate	1.40%	3.20%