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	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 33,332	$ 92,853
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	267	1,730
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	273,401	268,034
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	6,315	9,846
Debt Securities, Available-for-sale, Unrealized Loss Position	306,733	360,887
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 6,582	$ 11,576
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions	10	47
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions	121	115
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions	131	162
Corporate Debt Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 13,124	$ 46,988
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	38	1,045
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	118,442	108,738
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3,368	4,361
Debt Securities, Available-for-sale, Unrealized Loss Position	131,566	155,726
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	3,406	5,406
Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	847
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	37
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	5,793	4,993
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	149	215
Debt Securities, Available-for-sale, Unrealized Loss Position	5,793	5,840
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	149	252
US Treasury Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	6,138
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	15
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	36,035	31,693
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	250	408
Debt Securities, Available-for-sale, Unrealized Loss Position	36,035	37,831
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	250	423
US Government-sponsored Enterprises Debt Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	6,388	6,478
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	110	110
Debt Securities, Available-for-sale, Unrealized Loss Position	6,388	6,478
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	110	110
US States and Political Subdivisions Debt Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	20,208	33,021
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	229	522
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	103,933	113,297
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,410	4,706
Debt Securities, Available-for-sale, Unrealized Loss Position	124,141	146,318
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	2,639	5,228
Debt Security, Government, Non-US
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,810	2,835
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	28	46
Debt Securities, Available-for-sale, Unrealized Loss Position	2,810	2,835
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 28	46
Redeemable Preferred Stock
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		5,859
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		111
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0
Debt Securities, Available-for-sale, Unrealized Loss Position		5,859
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss		$ 111