Fair Value Measurements and Derivative Instrument (Recurring Fair Value Measurements) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (mutual funds)	$ 1,294	$ 1,477
Derivative stock appreciation rights	83,670	29,700
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (mutual funds)	1,294	1,477
Derivative stock appreciation rights	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (mutual funds)	0	0
Derivative stock appreciation rights	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation plan assets (mutual funds)	0	0
Derivative stock appreciation rights	$ 83,670	$ 29,700