Note 7. Employee Benefit Plans (Detail) - Net Periodic Pension Cost (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Benefits [Member]
Service cost	$ 993	$ 969	$ 2,980	$ 2,908
Interest cost	1,017	1,028	3,051	3,085
Expected return on plan assets	(1,145)	(1,370)	(3,435)	(4,111)
Amortization of prior service cost	101	101	301	302
Amortization of net (gain) loss	706	220	2,119	660
Net periodic benefit cost	1,672	948	5,016	2,844
Other Benefits [Member]
Service cost	17	14	51	41
Interest cost	19	19	58	58
Expected return on plan assets	(22)	(22)
Amortization of prior service cost	48	55	33	33
Amortization of net (gain) loss	(22)	(32)	(22)	(32)
Net periodic benefit cost	$ 40	$ 34	$ 120	$ 100