Investment Securities - Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due after one year through five years	$ 57,188
Total contractual maturities	57,188
Amortized Cost	4,014,397	$ 4,080,663
Fair Value
Due after one year through five years	57,648
Total contractual maturities	57,648
Fair value	4,058,457	4,075,644
Mortgage-backed securities:
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	858,264
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	883,414
Residential - Government agency
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	269,947
Amortized Cost	269,947	290,131
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	278,963
Fair value	278,963	291,209
Residential - Government-sponsored enterprises
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	403,682
Amortized Cost	403,682	395,039
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	417,667
Fair value	417,667	399,492
Commercial - Government-sponsored enterprises
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	184,635
Amortized Cost	184,635	101,798
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	186,784
Fair value	186,784	101,719
Collateralized mortgage obligations
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	3,098,945
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	3,117,395
Government agency
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	2,304,803
Amortized Cost	2,304,803	2,390,143
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	2,320,878
Fair value	2,320,878	2,381,278
Government-sponsored enterprises
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	794,142
Amortized Cost	794,142	772,023
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	796,517
Fair value	$ 796,517	$ 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).

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