Investment Securities - Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized Cost
Due after one year through five years	$ 523,117
Due after five years through ten years	114,725
Due after ten years	19,854
Total contractual maturities	657,696
Mortgage- and asset-backed securities	3,982,723
Amortized Cost	4,640,419	$ 5,357,275
Fair Value
Due after one year through five years	521,453
Due after five years through ten years	109,611
Due after ten years	19,854
Total contractual maturities	650,918
Mortgage- and asset-backed securities	3,847,424
Fair value	4,498,342	5,234,658
Government agency mortgage-backed securities
Amortized Cost
Mortgage- and asset-backed securities	426,710
Amortized Cost	426,710	356,858
Fair Value
Mortgage- and asset-backed securities	411,536
Fair value	411,536	351,390
Government-sponsored enterprises mortgage-backed securities
Amortized Cost
Mortgage- and asset-backed securities	156,056
Amortized Cost	156,056	178,702
Fair Value
Mortgage- and asset-backed securities	150,847
Fair value	150,847	174,741
Collateralized mortgage obligations: Government agency
Amortized Cost
Mortgage- and asset-backed securities	2,779,620
Amortized Cost	2,779,620	3,367,173
Fair Value
Mortgage- and asset-backed securities	2,682,449
Fair value	2,682,449	3,290,474
Collateralized mortgage obligations: Government-sponsored enterprises
Amortized Cost
Mortgage- and asset-backed securities	620,337
Amortized Cost	620,337	779,911
Fair Value
Mortgage- and asset-backed securities	602,592
Fair value	$ 602,592	$ 762,718

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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