Investments Unrealized Losses Less Than and Greater Than 12 Months (Details) $ in Thousands	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities In Continuous Loss Less Than 12 Months Fair Value		$ 124,789
Debt Securities Continuous Loss Position Less Than 12 Months Unrealized Losses		$ 1,092
Number of Debt Securities In Continuous Loss Less Than 12 Months		104
Debt Securities In Continuous Loss Position 12 Months Or Longer, Fair Value		$ 64,670
Debt Securities In Continuous Loss Position 12 Months Or Longer, Unrealized Losses		$ 3,292
Number of Debt Securities In Continuous Loss Position 12 Months or Longer		76
Debt Securities In Continuous Loss Position, Aggregate Fair Value		$ 189,459
Debt Securities In Continuous Loss Position, Aggregate Unrealized Losses		$ 4,384
Number of Debt Securities In Continuous Loss Position, Aggregate		180
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 227,132	$ 49,408
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 883	$ 312
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	233	46
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 33,891	$ 47,233
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 607	$ 1,228
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	46	46
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 261,023	$ 96,641
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 1,490	$ 1,540
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	279	92
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		$ 14,178
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 45
Number of Held to Maturity Securities In Continuous Loss Position Less Than 12 Months		15
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		$ 7,460
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ 584
Number of Held to Maturity Securities In Continuous Loss Position 12 Months or Greater		14
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		$ 21,638
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		$ 629
Number of Held to Maturity Securities In Continuous Loss Position Aggregate		29
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 230,030	$ 61,071
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 8,770	$ 732
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	191	39
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 9,936	$ 7,651
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 976	$ 820
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	8	10
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 239,966	$ 68,722
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 9,746	$ 1,552
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	199	49
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		$ 0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 0
Number of Held to Maturity Securities In Continuous Loss Position Less Than 12 Months		0
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		$ 2,169
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ 658
Number of Held to Maturity Securities In Continuous Loss Position 12 Months or Greater		2
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		$ 2,169
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		$ 658
Number of Held to Maturity Securities In Continuous Loss Position Aggregate		2
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 14,992
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 66
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	11
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	$ 14,992
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 66
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	11
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 18	$ 132
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 0	$ 3
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	3	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 98	$ 157
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 2	$ 2
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	4	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 116	$ 289
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 2	$ 5
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	7	8
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 3,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 8
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	4
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	$ 3,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 8
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	4
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 475,919	$ 110,611
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 9,727	$ 1,047
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	442	89
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 43,925	$ 55,041
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 1,585	$ 2,050
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	58	60
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 519,844	$ 165,652
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss	$ 11,312	$ 3,097
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	500	149
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		$ 14,178
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 45
Number of Held to Maturity Securities In Continuous Loss Position Less Than 12 Months		15
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		$ 9,629
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ 1,242
Number of Held to Maturity Securities In Continuous Loss Position 12 Months or Greater		16
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value		$ 23,807
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss		$ 1,287
Number of Held to Maturity Securities In Continuous Loss Position Aggregate		31
Preferred Stock [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 95
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		1
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		$ 95
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1
Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 95
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		1
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		$ 95
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1