Employee Benefits (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Fair Value Assumptions:      
Weighted average fair value of awards issued $ 5.22 $ 4.26 $ 3.71
Expected volatility 46.96% 47.72% 69.87%
Expected dividends 2.52% 2.87% 1.30%
Risk-free rate 1.55% 0.98% 0.62%
Expected term (years) 4 years 6 months 4 years 4 years