Fair Value Disclosures [Text Block]: Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Short-term Investments	$ 50	$ 50
Deposit Contracts, Liabilities	143,802	143,537
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 1
Short-term Investments	50	50
Deposit Contracts, Liabilities	0	0
Estimate of Fair Value Measurement | Fair Value, Inputs, Level 2
Short-term Investments	0	0
Deposit Contracts, Liabilities	143,954	143,702
Reported Value Measurement
Short-term Investments	50	50
Deposit Contracts, Liabilities	$ 143,802	$ 143,537