Incentive Plans (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Stock option [Abstract]
Exercised (in shares)	0	0
Information relating to 1993 Plan [Abstract]
Common shares reserved for issuance (in shares)			4,320,000
1993 Stock Incentive Plan [Member] | Stock Option [Member]
Stock option [Abstract]
Exercised (in shares)	0
Stock option grants (in shares)	0	0
Stock options exercisable (in shares)			0	0
Stock options outstanding (in shares)	0	0	0	0
Outstanding at end of period (in shares)	0	0