Note 5. Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligation	$ 18,820	$ 17,506	$ 56,458	$ 52,517
Expected return on plan assets	(23,319)	(22,831)	(69,955)	(68,493)
Amortization of actuarial gain (loss)	2,424	4,568	7,274	13,704
Amortization of prior-service costs (credits)	405	418	1,214	1,253
Net periodic benefit expense (income)	(1,670)	(339)	(5,009)	(1,019)
Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligation	862	803	2,588	2,410
Amortization of actuarial gain (loss)	219	280	657	839
Amortization of prior-service costs (credits)	2	1	4	4
Net periodic benefit expense (income)	1,083	1,084	3,249	3,253
Postretirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	170	370	712	1,112
Interest cost on benefit obligation	708	869	2,051	2,608
Amortization of actuarial gain (loss)	(271)	0	(1,584)	0
Amortization of prior-service costs (credits)	(715)	(263)	(2,147)	(789)
Net periodic benefit expense (income)	$ (108)	$ 976	$ (968)	$ 2,931