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	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 92,853	$ 249,475
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,730	2,931
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	268,034	135,465
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9,846	4,406
Debt Securities, Available-for-sale, Unrealized Loss Position	360,887	384,940
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 11,576	$ 7,337
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions	47	60
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions	115	76
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions	162	136
Corporate Debt Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 46,988	$ 85,642
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,045	1,250
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	108,738	44,640
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,361	1,597
Debt Securities, Available-for-sale, Unrealized Loss Position	155,726	130,282
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	5,406	2,847
Collateralized Mortgage Backed Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	847	1,381
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	37	45
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	4,993	5,237
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	215	135
Debt Securities, Available-for-sale, Unrealized Loss Position	5,840	6,618
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	252	180
US Treasury Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	6,138	75,811
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	15	198
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	31,693	9,302
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	408	198
Debt Securities, Available-for-sale, Unrealized Loss Position	37,831	85,113
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	423	396
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	6,478	9,669
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	110	205
Debt Securities, Available-for-sale, Unrealized Loss Position	6,478	9,669
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	110	205
US States and Political Subdivisions Debt Securities
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	33,021	83,682
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	522	1,348
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	113,297	66,617
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4,706	2,271
Debt Securities, Available-for-sale, Unrealized Loss Position	146,318	150,299
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	5,228	3,619
Debt Security, Government, Non-US
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	2,959
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	90
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,835	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	46	0
Debt Securities, Available-for-sale, Unrealized Loss Position	2,835	2,959
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	46	$ 90
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