Investments Unrealized Losses Less Than and Greater Than 12 Months (Details) $ in Thousands	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Debt Securities In Continuous Loss Less Than 12 Months Fair Value	$ 124,789	$ 341,677
Debt Securities Continuous Loss Position Less Than 12 Months Unrealized Losses	$ 1,092	$ 8,666
Number of Debt Securities In Continuous Loss Less Than 12 Months	104	308
Debt Securities In Continuous Loss Position 12 Months Or Longer, Fair Value	$ 64,670	$ 16,905
Debt Securities In Continuous Loss Position 12 Months Or Longer, Unrealized Losses	$ 3,292	$ 2,871
Number of Debt Securities In Continuous Loss Position 12 Months or Longer	76	21
Debt Securities In Continuous Loss Position, Aggregate Fair Value	$ 189,459	$ 358,582
Debt Securities In Continuous Loss Position, Aggregate Unrealized Losses	$ 4,384	$ 11,537
Number of Debt Securities In Continuous Loss Position, Aggregate	180	329
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 49,408	$ 202,788
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 312	$ 3,513
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	46	184
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 47,233	$ 8,018
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 1,228	$ 1,509
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	46	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 96,641	$ 210,806
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,540	$ 5,022
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	92	192
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 14,178	$ 43,659
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 45	$ 1,562
Number of Held to Maturity Securities In Continuous Loss Position Less Than 12 Months	15	47
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 7,460	$ 509
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 584	$ 37
Number of Held to Maturity Securities In Continuous Loss Position 12 Months or Greater	14	1
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	$ 21,638	$ 44,168
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 629	$ 1,599
Number of Held to Maturity Securities In Continuous Loss Position Aggregate	29	48
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 61,071	$ 91,527
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 732	$ 3,578
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	39	70
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 7,651	$ 6,102
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 820	$ 644
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	10	8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 68,722	$ 97,629
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,552	$ 4,222
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	49	78
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 0	$ 3,587
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 0	$ 12
Number of Held to Maturity Securities In Continuous Loss Position Less Than 12 Months	0	3
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 2,169	$ 2,171
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 658	$ 680
Number of Held to Maturity Securities In Continuous Loss Position 12 Months or Greater	2	2
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	$ 2,169	$ 5,758
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 658	$ 692
Number of Held to Maturity Securities In Continuous Loss Position Aggregate	2	5
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 132	$ 116
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 3	$ 1
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	4	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 157	$ 105
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 2	$ 1
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	4	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 289	$ 221
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 5	$ 2
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	8	6
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 110,611	$ 294,431
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 1,047	$ 7,092
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	89	258
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 55,041	$ 14,225
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 2,050	$ 2,154
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	60	18
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 165,652	$ 308,656
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 3,097	$ 9,246
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	149	276
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 14,178	$ 47,246
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 45	$ 1,574
Number of Held to Maturity Securities In Continuous Loss Position Less Than 12 Months	15	50
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 9,629	$ 2,680
Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 1,242	$ 717
Number of Held to Maturity Securities In Continuous Loss Position 12 Months or Greater	16	3
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value	$ 23,807	$ 49,926
Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,287	$ 2,291
Number of Held to Maturity Securities In Continuous Loss Position Aggregate	31	53
Bond Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 10,160
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 108
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		2
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 in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 10,160
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 108
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		2
Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 95	$ 201
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 6	$ 2
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	1	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0	$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 95	$ 201
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 6	$ 2
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1	2
Common Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		0
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		$ 17
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 17
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 95	$ 10,361
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 6	$ 110
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	1	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 0	$ 17
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	0	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 95	$ 10,361
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 6	$ 127
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1	5