Investment Securities (Schedule of Maturities of Investment Securities Available for Sale) (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 953,629
Due after one year through five years, Amortized Cost	5,310,095
Due after five years through ten years, Amortized Cost	2,347,332
Due after ten years, Amortized Cost	516,246
Amortized Cost	9,127,302
Due in one year or less, Fair Value	962,853
Due after one year through five years, Fair Value	5,314,711
Due after five years through ten years, Fair Value	2,385,896
Due after ten years, Fair Value	525,817
Fair Value	$ 9,189,277

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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