Securities Held to Maturity (Summary of Credit Rating) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	$ 99,457	$ 99,914
Marketable Securities [Line Items]
Debt Securities, Held-to-maturity	99,457	99,914
Standard & Poor's, AAA Rating
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	13,257	15,735
Marketable Securities [Line Items]
Debt Securities, Held-to-maturity	13,257	15,735
Standard & Poor's, AA Rating
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	78,631	76,585
Marketable Securities [Line Items]
Debt Securities, Held-to-maturity	78,631	76,585
Standard & Poor's, A Rating
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	7,569	7,594
Marketable Securities [Line Items]
Debt Securities, Held-to-maturity	7,569	7,594
Standard & Poor's, BBB Rating
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	0	0
Marketable Securities [Line Items]
Debt Securities, Held-to-maturity	0	0
Standard & Poor's, Below Investment Grade Rating
Investments, Debt and Equity Securities [Abstract]
Debt Securities, Held-to-maturity	0	0
Marketable Securities [Line Items]
Debt Securities, Held-to-maturity	$ 0	$ 0