Investment Securities - Amortized Cost and Fair Value, by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost
Due after one year through five years	$ 38,244
Due after five years through ten years	83,560
Due after ten years	48,319
Total contractual maturities	170,123
Amortized Cost	5,985,031	$ 4,080,663
Fair Value
Due after one year through five years	38,757
Due after five years through ten years	84,129
Due after ten years	48,535
Total contractual maturities	171,421
Fair value	6,071,415	4,075,644
Mortgage-backed securities:
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	2,103,778
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	2,139,469
Residential - Government agency
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	155,169
Amortized Cost	155,169	290,131
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	160,462
Fair value	160,462	291,209
Residential - Government-sponsored enterprises
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	434,282
Amortized Cost	434,282	395,039
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	447,200
Fair value	447,200	399,492
Commercial - Government agency
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	583,232
Amortized Cost	583,232
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	599,650
Fair value	599,650
Commercial - Government-sponsored enterprises
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	931,095
Amortized Cost	931,095	101,798
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	932,157
Fair value	932,157	101,719
Collateralized mortgage obligations
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	3,711,130
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	3,760,525
Government agency
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,902,326
Amortized Cost	1,902,326	2,390,143
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,933,553
Fair value	1,933,553	2,381,278
Government-sponsored enterprises
Amortized Cost
Mortgaged-backed securities and collateralized mortgage obligations	1,808,804
Amortized Cost	1,808,804	772,023
Fair Value
Mortgaged-backed securities and collateralized mortgage obligations	1,826,972
Fair value	$ 1,826,972	$ 770,619

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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