XML 50 R32.htm IDEA: XBRL DOCUMENT v3.8.0.1
Fair Value of Financial Instruments (Unrealized gain loss on trading securities held in Rabbi Trust) (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Fair Value of Financial Instruments [Abstract]    
Unrealized gains (losses) on trading securities held in rabbi trust $ (1,623) $ 463