Securities - Estimated Fair Value and Unrealized Loss for Securities Available-for-Sale and Held-to-Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available-for-sale, less than 12 months, estimated fair value	$ 57,192	$ 21,795
Available-for-sale, less than 12 months, unrealized losses	(48)	(6)
Available-for-sale, 12 months or longer, estimated fair value	0	0
Available-for-sale, 12 months or longer, unrealized losses	0	0
Available-for-sale, total, estimated fair value	57,192	21,795
Available-for-sale, total, unrealized losses	(48)	(6)
Held-to-maturity, less than 12 months, estimated fair value	419,591	86,523
Held-to-maturity, less than 12 months, unrealized losses	(8,391)	(546)
Held-to-maturity, 12 months or longer, estimated fair value	12,975	46,965
Held-to-maturity, 12 months or longer, unrealized losses	(367)	(2,680)
Held-to-maturity, total, estimated fair value	432,566	133,488
Held-to-maturity, total, unrealized losses	(8,758)	(3,226)
Total securities, less than 12 months, estimated fair value	476,783	108,318
Total securities, less than 12 months, unrealized losses	(8,439)	(552)
Total securities, 12 months or longer, estimated fair value	12,975	46,965
Total securities, 12 months or longer, unrealized losses	(367)	(2,680)
Total securities, estimated fair value	489,758	155,283
Total securities, unrealized losses	(8,806)	(3,232)
U.S. government and agency obligations | Securities investment
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available-for-sale, less than 12 months, estimated fair value	10,139	17,029
Available-for-sale, less than 12 months, unrealized losses	(8)	(2)
Available-for-sale, 12 months or longer, estimated fair value	0	0
Available-for-sale, 12 months or longer, unrealized losses	0	0
Available-for-sale, total, estimated fair value	10,139	17,029
Available-for-sale, total, unrealized losses	(8)	(2)
CLOs
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available-for-sale, less than 12 months, estimated fair value		4,766
Available-for-sale, less than 12 months, unrealized losses		(4)
Available-for-sale, 12 months or longer, estimated fair value		0
Available-for-sale, 12 months or longer, unrealized losses		0
Available-for-sale, total, estimated fair value		4,766
Available-for-sale, total, unrealized losses		(4)
CLOs | Securities investment
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available-for-sale, less than 12 months, estimated fair value	47,053
Available-for-sale, less than 12 months, unrealized losses	(40)
Available-for-sale, 12 months or longer, estimated fair value	0
Available-for-sale, 12 months or longer, unrealized losses	0
Available-for-sale, total, estimated fair value	47,053
Available-for-sale, total, unrealized losses	(40)
State, municipal and sovereign debt obligations | Securities investment
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	50,696	2,823
Held-to-maturity, less than 12 months, unrealized losses	(890)	(23)
Held-to-maturity, 12 months or longer, estimated fair value	5,748	7,509
Held-to-maturity, 12 months or longer, unrealized losses	(216)	(208)
Held-to-maturity, total, estimated fair value	56,444	10,332
Held-to-maturity, total, unrealized losses	(1,106)	(231)
Corporate debt securities | Securities investment
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	39,041	10,192
Held-to-maturity, less than 12 months, unrealized losses	(1,774)	(255)
Held-to-maturity, 12 months or longer, estimated fair value	3,818	35,935
Held-to-maturity, 12 months or longer, unrealized losses	(138)	(2,397)
Held-to-maturity, total, estimated fair value	42,859	46,127
Held-to-maturity, total, unrealized losses	(1,912)	(2,652)
Mortgage-backed securities - FNMA
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	329,854	73,508
Held-to-maturity, less than 12 months, unrealized losses	(5,727)	(268)
Held-to-maturity, 12 months or longer, estimated fair value	3,409	3,521
Held-to-maturity, 12 months or longer, unrealized losses	(13)	(75)
Held-to-maturity, total, estimated fair value	333,263	77,029
Held-to-maturity, total, unrealized losses	(5,740)	(343)
Mortgage-backed securities - FNMA | FHLMC
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	158,632	24,661
Held-to-maturity, less than 12 months, unrealized losses	(3,178)	(117)
Held-to-maturity, 12 months or longer, estimated fair value	0	669
Held-to-maturity, 12 months or longer, unrealized losses	0	(7)
Held-to-maturity, total, estimated fair value	158,632	25,330
Held-to-maturity, total, unrealized losses	(3,178)	(124)
Mortgage-backed securities - FNMA | FNMA
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	163,103	39,365
Held-to-maturity, less than 12 months, unrealized losses	(2,478)	(128)
Held-to-maturity, 12 months or longer, estimated fair value	293	939
Held-to-maturity, 12 months or longer, unrealized losses	(3)	(19)
Held-to-maturity, total, estimated fair value	163,396	40,304
Held-to-maturity, total, unrealized losses	(2,481)	(147)
Mortgage-backed securities - FNMA | GNMA
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	6,104	5,856
Held-to-maturity, less than 12 months, unrealized losses	(23)	(11)
Held-to-maturity, 12 months or longer, estimated fair value	0	207
Held-to-maturity, 12 months or longer, unrealized losses	0	(1)
Held-to-maturity, total, estimated fair value	6,104	6,063
Held-to-maturity, total, unrealized losses	(23)	(12)
Mortgage-backed securities - FNMA | SBA
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held-to-maturity, less than 12 months, estimated fair value	2,015	3,626
Held-to-maturity, less than 12 months, unrealized losses	(48)	(12)
Held-to-maturity, 12 months or longer, estimated fair value	3,116	1,706
Held-to-maturity, 12 months or longer, unrealized losses	(10)	(48)
Held-to-maturity, total, estimated fair value	5,131	5,332
Held-to-maturity, total, unrealized losses	$ (58)	$ (60)