Fair Value Disclosures [Text Block]: Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Short-term investments	$ 50	$ 6,912
Deposit Contracts, Liabilities	143,537	145,749
Estimate of Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 1
Short-term investments	50	6,912
Deposit Contracts, Liabilities	0	0
Estimate of Fair Value, Fair Value Disclosure | Fair Value, Inputs, Level 2
Short-term investments	0	0
Deposit Contracts, Liabilities	143,702	146,098
Carrying (Reported) Amount, Fair Value Disclosure
Short-term investments	50	6,912
Deposit Contracts, Liabilities	$ 143,537	$ 145,749