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Shareholders' Equity (Details 4) - Class A common shares - $ / shares
6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award    
Weighted average fair value $ 4.57 $ 4.89
Expected term (years) 7 years 7 years
Dividend Yield 3.00% 3.00%
Volatility 35.90% 37.30%
Risk-free interest rate 1.90% 2.20%