Securities - Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Less than 12 Months	$ 122,666	$ 47,880
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, 12 Months or Longer	14,996	192,275
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	137,662	240,155
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Less than 12 Months	193	202
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, 12 Months or Longer	3	880
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Total	196	1,082
Treasury notes
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Less than 12 Months		1,990
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, 12 Months or Longer		995
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total		2,985
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Less than 12 Months		8
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, 12 Months or Longer		5
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Total		13
Federal agencies
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Less than 12 Months	121,552	28,296
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, 12 Months or Longer	14,996	191,280
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	136,548	219,576
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Less than 12 Months	190	97
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, 12 Months or Longer	3	875
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Total	193	972
Municipals
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Less than 12 Months		2,051
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total		2,051
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Less than 12 Months		18
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Total		18
Mortgage-backed - Government-sponsored entity (GSE) - residential
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value
Available-for-sale securities, Continuous Unrealized Loss Position, Fair Value, Less than 12 Months	1,114	15,543
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	1,114	15,543
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Less than 12 Months	3	79
Available-for-sale securities, Continuous Unrealized Loss Position, Gross Unrealized Losses, Total	$ 3	$ 79