Note 5. Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligation	$ 18,767	$ 17,422	$ 37,638	$ 35,011
Expected return on plan assets	(23,309)	(23,005)	(46,636)	(45,662)
Amortization of actuarial gain (loss)	2,375	4,486	4,850	9,136
Amortization of prior-service costs (credits)	405	417	809	835
Net periodic benefit expense (income)	(1,762)	(680)	(3,339)	(680)
Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost on benefit obligation	864	803	1,726	1,607
Amortization of actuarial gain (loss)	219	280	438	559
Amortization of prior-service costs (credits)	1	2	2	3
Net periodic benefit expense (income)	1,084	1,085	2,166	2,169
Postretirement Medical Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	271	313	542	742
Interest cost on benefit obligation	671	848	1,343	1,739
Amortization of actuarial gain (loss)	(656)	0	(1,313)	0
Amortization of prior-service costs (credits)	(716)	(263)	(1,432)	(526)
Net periodic benefit expense (income)	$ (430)	$ 898	$ (860)	$ 1,955