Note 7. Employee Benefit Plans (Detail) - Net Periodic Pension Cost (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits [Member]
Service cost	$ 993	$ 969
Interest cost	1,017	1,028
Expected return on plan assets	(1,145)	(1,370)
Amortization of prior service cost	100	101
Amortization of net (gain) loss	707	220
Net periodic benefit cost	1,672	948
Other Benefits [Member]
Service cost	17	14
Interest cost	19	19
Amortization of prior service cost	11	11
Amortization of net (gain) loss	(7)	(11)
Net periodic benefit cost	$ 40	$ 33