Fair Value Measurements (Narrative) (Details) - Recurring [Member] - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Fair Value of Financial Instruments, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Transfers of assets and liabilities between levels	$ 0	$ 0
Visa Inc [Member]
Fair Value of Financial Instruments, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Number of shares of Visa Class B common stock	192,163
Investment Securities [Member] | Minimum [Member]
Fair Value of Financial Instruments, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Targeted duration	2 years
Investment Securities [Member] | Maximum [Member]
Fair Value of Financial Instruments, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Targeted duration	5 years 6 months