Fair Value Measurements (Summary Of Quantitative Information About Level 3 Fair Value Measurements) (Details)	3 Months Ended
	Mar. 31, 2022 Rate
Fair Value Assets Measured on Recurring Basis [Line Items]
Valuation Technique, Discounted cash flow	Discounted cash flow
Auction rate securities
Fair Value Assets Measured on Recurring Basis [Line Items]
Valuation Technique, Discounted cash flow	Discounted cash flow
Estimated market recovery period	5 years
Auction rate securities | Minimum [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
Estimated market rate	2.50%
Auction rate securities | Maximum [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
Estimated market rate	3.00%
Auction rate securities | Weighted Average [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
Estimated market recovery period	5 years	[1]
Estimated market rate	2.80%	[1]
Private Equity Investments
Fair Value Assets Measured on Recurring Basis [Line Items]
Valuation Technique, Market comparable companies	Market comparable companies
Private Equity Investments | Minimum [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
EBITDA multiple	4.0
Private Equity Investments | Maximum [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
EBITDA multiple	6.0
Private Equity Investments | Weighted Average [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
EBITDA multiple	5.4	[1]
Mortgage loan commitments
Fair Value Assets Measured on Recurring Basis [Line Items]
Valuation Technique, Discounted cash flow	Discounted cash flow
Mortgage loan commitments | Minimum [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
Probability of funding	68.20%
Embedded servicing value	0.00%
Mortgage loan commitments | Maximum [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
Probability of funding	100.00%
Embedded servicing value	1.40%
Mortgage loan commitments | Weighted Average [Member]
Fair Value Assets Measured on Recurring Basis [Line Items]
Probability of funding	90.20%	[1]
Embedded servicing value	1.10%	[1]

[1] * Unobservable inputs were weighted by the relative fair value of the instruments.