Earnings Per Share: Earnings Per Share Reconciliation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income available for common stock	$ 93,174	$ 103,808
Weighted average shares - basic (in shares)	61,778	59,920
Dilutive effect of:
Equity compensation (in shares)	78	140
Weighted average shares - diluted (in shares)	61,856	60,060
Earnings (loss) per share, Basic (usd per share)	$ 1.51	$ 1.73
Earnings (loss) per share, Diluted (usd per share)	$ 1.51	$ 1.73