Debt Securities Available for Sale - Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,132,936	$ 1,086,143
Gross Unrealized Gains	46,816	14,248
Gross Unrealized (Losses)	(1,827)	(2,055)
Debt securities available for sale, at fair value	1,177,925	1,098,336
U.S. government and agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	35,433	42,081
Gross Unrealized Gains	1,238	321
Gross Unrealized (Losses)	0	(16)
Debt securities available for sale, at fair value	36,671	42,386
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,013,079	968,165
Gross Unrealized Gains	43,526	12,981
Gross Unrealized (Losses)	(377)	(1,265)
Debt securities available for sale, at fair value	1,056,228	979,881
Municipal obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,873	2,284
Gross Unrealized Gains	14	1
Gross Unrealized (Losses)	0	(1)
Debt securities available for sale, at fair value	1,887	2,284
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	77,551	68,613
Gross Unrealized Gains	2,038	945
Gross Unrealized (Losses)	(749)	(378)
Debt securities available for sale, at fair value	78,840	69,180
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,000	5,000
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(701)	(395)
Debt securities available for sale, at fair value	$ 4,299	$ 4,605

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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