Stock Based Compensation and Other Benefit Plans - Stock Appreciation Rights Activity (Details) - Stock Appreciation Rights (SARs) [Member]	12 Months Ended
	Dec. 31, 2017 shares
Outstanding at beginning of period (in shares)	69,500
Exercised (in shares)	(25,000)
Expired or cancelled (in shares)	(1,500)
Outstanding at end of period (in shares)	43,000
Exercisable at end of period (in shares)	43,000