v3.3.1.900
Equity Option Valuation Assumptions (Details) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Valuation Assumptions [Abstract]      
Expected period that options will be outstanding (in years) 5 years 7 days 4 years 10 months 13 days 4 years 10 months 25 days
Interest rate (based on U.S. Treasury yields at the time of grant) 1.62% 1.62% 1.06%
Volatility 28.75% 34.67% 43.22%
Dividend yield 0.00% 0.00% 0.00%
Weighted-average fair value of options granted $ 11.87 $ 22.65 $ 18.07