v3.3.1.900
Share Compensation and Pension Plans - Assumptions Used in Determining Fair Value of Options Granted (Details)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Assumptions:      
Volatility, maximum 37.60% 51.40% 51.40%
Volatility, minimum     45.30%
Risk-free interest rate, maximum 1.55% 1.77% 1.77%
Risk-free interest rate, minimum     0.85%
Weighted average expected lives 5 years 6 months 6 years 1 month 6 days 6 years 1 month 6 days
Forfeiture rate, minimum 2.16% 3.45% 1.60%
Dividend yield rate 4.05% 3.46%  
Maximum      
Assumptions:      
Forfeiture rate, minimum     3.45%
Dividend yield rate     3.55%
Minimum      
Assumptions:      
Dividend yield rate     3.46%