Investment Securities - Number, Fair Value and Gross Unrealized Losses (Details) $ in Thousands	Dec. 31, 2020 USD ($) investmentSecurity	Dec. 31, 2019 USD ($) investmentSecurity
Number
Less than 12 months | investmentSecurity	106	45
12 months or Longer | investmentSecurity	10	21
Total | investmentSecurity	116	66
Fair Value
Less than 12 months	$ 812,988	$ 274,640
12 months or Longer	10,865	41,003
Total	823,853	315,643
Gross Unrealized Losses
Less than 12 months	(5,319)	(3,258)
12 months or Longer	(303)	(834)
Total	$ (5,622)	$ (4,092)
U.S. Treasury
Number
Less than 12 months | investmentSecurity		1
12 months or Longer | investmentSecurity		0
Total | investmentSecurity		1
Fair Value
Less than 12 months		$ 10,194
12 months or Longer		0
Total		10,194
Gross Unrealized Losses
Less than 12 months		(39)
12 months or Longer		0
Total		$ (39)
Agency
Number
Less than 12 months | investmentSecurity	4	13
12 months or Longer | investmentSecurity	9	9
Total | investmentSecurity	13	22
Fair Value
Less than 12 months	$ 74,194	$ 102,874
12 months or Longer	10,434	13,514
Total	84,628	116,388
Gross Unrealized Losses
Less than 12 months	(307)	(1,340)
12 months or Longer	(301)	(336)
Total	$ (608)	$ (1,676)
Corporate
Number
Less than 12 months | investmentSecurity	9	1
12 months or Longer | investmentSecurity	0	0
Total | investmentSecurity	9	1
Fair Value
Less than 12 months	$ 71,226	$ 1,017
12 months or Longer	0	0
Total	71,226	1,017
Gross Unrealized Losses
Less than 12 months	(506)	(14)
12 months or Longer	0	0
Total	$ (506)	$ (14)
Municipal bonds
Number
Less than 12 months | investmentSecurity	56	12
12 months or Longer | investmentSecurity	0	0
Total | investmentSecurity	56	12
Fair Value
Less than 12 months	$ 312,894	$ 30,541
12 months or Longer	0	0
Total	312,894	30,541
Gross Unrealized Losses
Less than 12 months	(3,253)	(184)
12 months or Longer	0	0
Total	$ (3,253)	$ (184)
Collateralized mortgage obligations
Number
Less than 12 months | investmentSecurity	21	0
12 months or Longer | investmentSecurity	1	1
Total | investmentSecurity	22	1
Fair Value
Less than 12 months	$ 215,603	$ 0
12 months or Longer	431	603
Total	216,034	603
Gross Unrealized Losses
Less than 12 months	(710)	0
12 months or Longer	(2)	(8)
Total	$ (712)	$ (8)
Mortgage-backed securities
Number
Less than 12 months | investmentSecurity	16	18
12 months or Longer | investmentSecurity	0	11
Total | investmentSecurity	16	29
Fair Value
Less than 12 months	$ 139,071	$ 130,014
12 months or Longer	0	26,886
Total	139,071	156,900
Gross Unrealized Losses
Less than 12 months	(543)	(1,681)
12 months or Longer	0	(490)
Total	$ (543)	$ (2,171)