INVESTMENT SECURITIES (HTM Debt Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 5,488,576	$ 3,938,797
Gross Unrealized Gains	181,256	31,469
Gross Unrealized Loss	(941)	(13,039)
Fair Value	5,668,891	3,957,227
ABS
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	50,381	0
Gross Unrealized Gains	561	0
Gross Unrealized Loss	0	0
Fair Value	50,942	0
GNMA - Residential
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,156,473	1,948,025
Gross Unrealized Gains	50,005	11,354
Gross Unrealized Loss	(801)	(7,670)
Fair Value	2,205,677	1,951,709
GNMA - Commercial
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	3,281,722	1,990,772
Gross Unrealized Gains	130,690	20,115
Gross Unrealized Loss	(140)	(5,369)
Fair Value	$ 3,412,272	$ 2,005,518