Investment Securities - Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less	$ 29,653
Due after one year through five years	126,696
Total contractual maturities	156,349
Amortized Cost	4,143,124	$ 4,640,419
Fair Value
Due in one year or less	29,738
Due after one year through five years	126,649
Total contractual maturities	156,387
Fair value	4,157,082	4,498,342
Government agency debt securities
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	24,387
Amortized Cost	24,387
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	24,472
Fair value	24,472
Government agency mortgage-backed securities
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	342,326
Amortized Cost	342,326	426,710
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	343,905
Fair value	343,905	411,536
Government-sponsored enterprises mortgage-backed securities
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	366,346
Amortized Cost	366,346	156,056
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	371,949
Fair value	371,949	150,847
Collateralized mortgage obligations: Government agency
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	2,479,961
Amortized Cost	2,479,961	2,779,620
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	2,486,524
Fair value	2,486,524	2,682,449
Collateralized mortgage obligations: Government-sponsored enterprises
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	773,755
Amortized Cost	773,755	620,337
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	773,845
Fair value	773,845	$ 602,592
Collateralized mortgage obligations
Amortized Cost
Government debt securities, mortgaged-backed securities and obligations	3,253,716
Fair Value
Government debt securities, mortgaged-backed securities and collateralized mortgage obligations	$ 3,260,369

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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