Selected Balance Sheet Information: Changes to Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss, Current	$ 7,585	$ 7,585	$ 5,086	$ 2,444	$ 3,209
Accounts Receivable, Credit Loss Expense (Reversal)		6,715	4,913
Accounts Receivable, Allowance for Credit Loss, Recovery		2,203	1,870
Accounts Receivable, Allowance for Credit Loss, Writeoff		(3,777)	$ (4,906)
Adjustment Related to COVID-19
Accounts Receivable, Credit Loss Expense (Reversal)	$ 1,500	$ 2,000