Interest-bearing Deposits and Securities: Schedule of Amortized Cost and Estimated Fair Value of Trading Securities by Contractual Maturity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Mortgage Backed Securities Contractual Maturity
Trading Securities Amortized Cost Contractual Maturity	$ 29,436	$ 34,024
Trading Securities Fair Value Contractual Maturity	32,063	36,673
Due in one year or less
Trading Securities Amortized Cost Contractual Maturity		1,000
Trading Securities Fair Value Contractual Maturity		1,009
Due after one year through five years
Trading Securities Amortized Cost Contractual Maturity	1,544	1,545
Trading Securities Fair Value Contractual Maturity	1,619	1,626
Due after five years through ten years
Trading Securities Amortized Cost Contractual Maturity	4,093	4,087
Trading Securities Fair Value Contractual Maturity	4,091	4,123
Due after ten years through twenty years
Trading Securities Amortized Cost Contractual Maturity	6,717	6,544
Trading Securities Fair Value Contractual Maturity	6,728	6,184
Due after twenty years
Trading Securities Amortized Cost Contractual Maturity	57,516	58,549
Trading Securities Fair Value Contractual Maturity	32,413	30,710
Total by contractual maturity before mortgage-backed and equity securities
Trading Securities Amortized Cost Contractual Maturity	69,870	71,725
Trading Securities Fair Value Contractual Maturity	44,851	43,652
Equity securities contractual maturity
Trading Securities Amortized Cost Contractual Maturity	6,914	6,914
Trading Securities Fair Value Contractual Maturity	454	402
Total by contractual maturity
Trading Securities Amortized Cost Contractual Maturity	106,220	112,663
Trading Securities Fair Value Contractual Maturity	$ 77,368	$ 80,727