Investment Securities, Securities Available-for-Sale (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021		Dec. 31, 2020	Mar. 31, 2020
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		$ 562,821		$ 789,175	$ 512,776
Gross unrealized gains		9,029		18,716	19,576
Gross unrealized losses		10,877		159	106
Fair/Book value		560,973		807,732	532,246
US Treasury Notes [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		14,885		14,859	14,777
Gross unrealized gains		348		429	622
Gross unrealized losses		0		0	0
Fair/Book value		15,233		15,288	15,399
US Government Agency SBA [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		7,894		8,252	10,043
Gross unrealized gains		1		1	9
Gross unrealized losses		86		93	98
Fair/Book value		7,809		8,160	9,954
Mortgage Backed Securities [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost	[1]	494,399	[2]	720,562	482,439
Gross unrealized gains	[1]	8,192	[2]	17,359	18,945
Gross unrealized losses	[1]	10,080	[2]	48	8
Fair/Book value	[1]	492,511	[2]	737,873	501,376
Securities Transferred [Abstract]
Fair value of securities transferred to held-to-maturity category		316,900
Corporate Securities [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		44,998		45,010
Gross unrealized gains		488		927
Gross unrealized losses		711		18
Fair/Book value		44,775		45,919
Other [Member]
Amortized cost, fair values, and unrealized gains and losses of securities available-for-sale [Abstract]
Amortized cost		645		492	5,517
Gross unrealized gains		0		0	0
Gross unrealized losses		0		0	0
Fair/Book value		$ 645		$ 492	$ 5,517

[1] All Mortgage Backed Securities were issued by an agency or government sponsored entity of the U.S. Government.All Mortgage Backed Securities were issued by an agency or government sponsored entity of the U.S. Government.

[2] During Q1 2021, the Company transferred $316.9 million of AFS securities to HTM.