Note 8. Employee Benefit Plans (Detail) - Change In Benefit Obligation (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	$ 76,925	$ 66,813
Service cost	3,877	2,203
Interest cost	4,114	3,724
Amendments	396
Actuarial loss	6,476	7,907
Benefits paid	(3,893)	(3,722)
Benefit obligation at end of year	87,895	76,925
Change in fair value of plan assets:
Fair value of plan assets at beginning of year	70,462	64,889
Actual return (loss) on plan assets	(1,818)	8,976
Employer contributions	331	319
Benefits paid	(3,893)	(3,722)
Fair value of plan assets at end of year	65,082	70,462
Funded status at end of year	(22,813)	(6,463)
Other Postretirement Benefit Plans, Defined Benefit [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	1,430	1,295
Service cost	54	46
Interest cost	77	73
Actuarial loss	127	40
Benefits paid	(17)	(24)
Benefit obligation at end of year	1,671	1,430
Change in fair value of plan assets:
Employer contributions	17	24
Benefits paid	(17)	(24)
Funded status at end of year	$ (1,671)	$ (1,430)