Selected Balance Sheet Information: Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Selected Balance Sheet Information [Abstract]
Accrued employee compensation, benefits and withholdings	$ 59,701	$ 62,837
Accrued property taxes	36,832	44,547
Customer deposits and prepayments	45,143	54,728
Accrued interest	31,757	31,868
Other (none of which is individually significant)	28,234	32,787
Total accrued liabilities	$ 201,667	$ 226,767