Securities (Scheduled Contractual Maturities of AFS Debt Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Amortized Cost
Due within one year	$ 1,403,404
Due after one year through five years	688,387
Due after five years through ten years	1,427,893
Due after ten years	4,384,862
Amortized Cost	7,904,546	$ 5,470,523
Fair Value
Due within one year	1,347,808
Due after one year through five years	681,602
Due after five years through ten years	1,414,362
Due after ten years	4,345,441
Total available-for-sale debt investment securities	7,789,213	5,544,658
Available for sale debt investment securities pledged as collateral, fair value	$ 590,858	$ 588,484

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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