Management's Statement: Management Statement (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 2,620,200	$ 2,614,496	$ 2,624,423		$ 2,464,069	$ 2,432,896	$ 2,419,998	$ 2,383,702	$ 2,287,423
Cumulative Effect, Period of Adoption, Adjustment
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			$ (207)	$ (200)		$ 3	$ (3)	$ 3,390