Note 4. Investment Securities: Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value (Details) $ in Thousands	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	$ 194,697	$ 210,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,541	3,709
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	100,763	91,565
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,853	4,512
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	295,460	301,922
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 6,394	$ 8,221
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	80	99
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	30	31
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	110	130
Corporate Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	$ 43,714	$ 101,903
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	687	2,559
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	71,655	55,217
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,157	3,309
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	115,369	157,120
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	4,844	5,868
US Treasury Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	104,478	19,809
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	7	64
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	104,478	19,809
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	7	64
US Government-sponsored Enterprises Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	3,578	6,539
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	66	128
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	6,907	4,997
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	142	126
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10,485	11,536
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	208	254
US States and Political Subdivisions Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	38,859	68,898
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	584	780
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	20,900	31,351
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	528	1,077
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	59,759	100,249
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	1,112	1,857
Redeemable Preferred Stock
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	3,590	3,749
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	173	14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,590	3,749
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	173	14
Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	194,219	204,249
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,517	3,565
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	99,462	91,565
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,827	4,512
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	293,681	295,814
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6,344	8,077
COMMON STOCK, AMOUNT
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	478	4,784
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24	142
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	478	4,784
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	24	142
Nonredeemable Preferred Stock
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value		1,324
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,301
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	26
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,301	1,324
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	26	2
Equity Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	478	6,108
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	24	144
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,301
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	26
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,779	6,108
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 50	144
Residential Mortgage Backed Securities Member
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value		2,867
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		2,867
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		14
Foreign Government Debt
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value		484
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		484
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 6