Investment Securities (Amortized Cost And Estimated Fair Value Of Investments In Debt Securities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 980,047	$ 1,187,499
Securities Available-for-Sale, Total Fair value	1,032,814	1,209,701
U.S. Government Sponsored Entities Asset-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	698,237	884,571
Securities Available-for-Sale, Total Fair value	$ 726,297	889,210
Available for Sale Securities Weighted Avg Yield	2.37%
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	$ 58,800
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	$ 64,264
Debt Securities, Available-for-sale, Maturity, after Five Through Ten Years, Weighted Average Yield	3.81%
Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost	$ 221,010
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value	$ 240,242
Debt Securities, Available-for-sale, Maturity, after 10 Years, Weighted Average Yield	3.67%
Debt Securities, Available-for-sale, Amortized Cost	$ 279,810	302,928
Securities Available-for-Sale, Total Fair value	$ 304,506	$ 320,491
Available for Sale Securities Weighted Avg Yield	3.70%
Corporate Debt Securities
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost	$ 2,000
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value	$ 2,011
Debt Securities, Available-for-sale, Maturity, after Five Through Ten Years, Weighted Average Yield	4.00%
Debt Securities, Available-for-sale, Amortized Cost	$ 2,000
Securities Available-for-Sale, Total Fair value	$ 2,011

Available for Sale Securities Weighted Avg Yield

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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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount 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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Weighted average yield of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing after tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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