Note 6. Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2015

Qualified Pension Plans [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

	Qualified Pension Plans
	Three Months Ended June 30,						Six Months Ended June 30,
(Dollars in thousands)	2015			2014			2015			2014
Interest cost on benefit obligation	$	18,211		$	18,767		$	36,392		$	37,638
Expected return on plan assets	(21,727		)	(23,309		)	(43,467		)	(46,636		)
Amortization of actuarial loss	3,241			2,375			6,364			4,850
Amortization of prior-service costs	404			405			809			809
Settlement loss (gain)	(22		)	—			38			—
Net periodic benefit expense (income)	$	107		$	(1,762	)	$	136		$	(3,339	)

Non Qualified Pension Plans [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

	Non-Qualified Pension Plan
	Three Months Ended June 30,				Six Months Ended June 30,
(Dollars in thousands)	2015		2014		2015		2014
Interest cost on benefit obligation	$	797	$	864	$	1,593	$	1,726
Amortization of actuarial loss	305		219		601		438
Amortization of prior-service costs	1		1		2		2
Net periodic benefit expense	$	1,103	$	1,084	$	2,196	$	2,166

Postretirement Medical Plan [Member]

Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]

Schedule of Net Benefit Costs [Table Text Block]

	Three Months Ended June 30,						Six Months Ended June 30,
(Dollars in thousands)	2015			2014			2015			2014
Service cost	$	171		$	271		$	464		$	542
Interest cost on benefit obligation	625			671			1,270			1,343
Amortization of actuarial gain	(176		)	(656		)	(241		)	(1,313		)
Amortization of prior-service credit	(613		)	(716		)	(1,227		)	(1,432		)
Net periodic benefit expense (income)	$	7		$	(430	)	$	266		$	(860	)