Incentive plans (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period to award Bonuses to Participants after end of fiscal year, maximum	0 years 0 months 120 days
Stock option [Roll Forward]
Exercised (in shares)	(680,000)	0
Information relating to 1993 Plan [Abstract]
Stock based compensation expense recorded for the year ended	$ 0	$ 120
Common shares reserved for issuance (in shares)	4,430,000
Stock Options [Member]
Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, exercised (in dollars per share)		$ 1.09
Information relating to 1993 Plan [Abstract]
Number of shares related to the extension of option expiration date (in shares)		200,000
Number of shares related to the extension of option expiration date		2 years
Exercise price of the stock options changed (in dollars per share)		$ 1.11
Exercise price of the stock options (in dollars per share)		$ 1.09
1993 Stock Incentive Plan [Member]
Information relating to 1993 Plan [Abstract]
Unamortized compensation cost relating to non-vested stock options	0	0
Stock based compensation expense recorded for the year ended	0	120
Options to purchase shares of common stock which were excluded from computation of diluted earnings per share due to the effect of being anti-dilutive in the computation of earnings per share.	0
Common shares reserved for issuance (in shares)	4,320,000
Shares available for future stock option grants (in shares)	4,320,000
Intrinsic value of options outstanding	0
Intrinsic value of options exercisable	$ 0
1993 Stock Incentive Plan [Member] | Stock Options [Member]
Stock option [Roll Forward]
Outstanding at beginning of period (in shares)	816,000	836,000
Exercised (in shares)	(680,000)
Expired (in shares)	(136,000)	(20,000)
Outstanding at end of period (in shares)	0	816,000
Exercisable at end of period (in shares)	0	816,000
Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price outstanding at beginning of period (in dollars per share)	$ 0.88	$ 0.87
Weighted average exercise price, expired (in dollars per share)	$ 1.09	$ 0.95
Weighted average exercise price, exercised (in dollars per share)	$ 0.84
Weighted average exercise price, outstanding at end of period (in dollars per share)		$ 0.88
Weighted average exercise price, exercisable at end of period (in dollars per share)	$ 0	$ 0.88
Information relating to 1993 Plan [Abstract]
Exercise price of the stock options (in dollars per share)	$ 0.84
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Weighted average fair value at grant date (in dollars per share)		$ 0.60
Estimated dividend yield (in hundredths)		0.00%
Risk free interest rate (in hundredths)		0.25%
Estimated volatility (in hundredths)		103.90%
Expected life in years		2 years