Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]: Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value (Details) $ in Thousands	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	$ 199,484	$ 331,210
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,764	9,284
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	89,175	48,785
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,344	2,980
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	288,659	379,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 6,108	$ 12,264
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	107	156
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	44	23
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	151	179
Corporate Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	$ 84,636	$ 145,205
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,087	3,818
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	25,563	19,841
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,384	1,672
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	110,199	165,046
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,471	5,490
Residential Mortgage Backed Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	4,730	5,038
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	101	116
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	2,105	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	5	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6,835	5,038
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	106	116
US Treasury Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	18,021	28,406
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	80	441
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	12,619	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	177	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	30,640	28,406
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	257	441
US Government-sponsored Enterprises Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	3,286	3,640
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	65	166
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	6,480	6,220
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	146	256
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	9,766	9,860
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	211	422
US States and Political Subdivisions Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	88,326	144,357
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,413	4,561
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	35,771	18,132
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,415	554
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	124,097	162,489
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	2,828	5,115
Foreign Government Debt
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	0	3,738
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	157
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	3,006	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	85	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,006	3,738
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	85	157
Redeemable Preferred Stock
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	3,631	3,315
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	132	448
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3,631	3,315
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	132	448
Debt Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	198,999	330,384
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,746	9,259
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	89,175	47,508
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,344	2,930
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	288,174	377,892
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	6,090	12,189
Common Stock
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	485
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	485
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	18
Equity Securities
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	485	826
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	18	25
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	1,277
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	50
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	485	2,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 18	75
Nonredeemable Preferred Stock
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value		826
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		25
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		1,277
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		50
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		2,103
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 75