Securities - Carrying Value of Held-to-Maturity Investment Securities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Amortized cost	$ 874,119	$ 772,975
Net loss on date of transfer from available-for-sale	(13,347)	(13,347)
Debt securities, held to maturity, allowance for credit losses	(2,446)	0
Accretion of net unrealized loss on securities reclassified as held-to-maturity	9,633	9,245
Carrying value	$ 867,959	$ 768,873