Securities - Securities with Unrealized Losses - Securities Held-to-maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Held-to-maturity, Fair Value
Less Than 12 Months	$ 51,616	$ 21,107
12 Months or More	88,128	313,218
Total	139,744	334,325
Held-to-maturity, Unrealized (Losses)
Less Than 12 Months	(182)	(130)
12 Months or More	(790)	(11,264)
Total	(972)	(11,394)
Agency mortgage-backed securities
Held-to-maturity, Fair Value
Less Than 12 Months	50,060	16,088
12 Months or More	88,128	255,917
Total	138,188	272,005
Held-to-maturity, Unrealized (Losses)
Less Than 12 Months	(178)	(103)
12 Months or More	(790)	(9,050)
Total	(968)	(9,153)
Municipals - exempt from Federal tax
Held-to-maturity, Fair Value
Less Than 12 Months	1,556	5,019
12 Months or More		57,301
Total	1,556	62,320
Held-to-maturity, Unrealized (Losses)
Less Than 12 Months	(4)	(27)
12 Months or More		(2,214)
Total	$ (4)	$ (2,241)