Benefit Plans (Fair Values Of Nonvested Performance Shares And Performance Units) (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Performance Shares Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	131,872
Performance Units Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	34,574
2018 Grant [Member] | Performance Shares Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	68,307
Estimated payout percentage based on performance criteria	118.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 64.57
2018 Grant [Member] | Performance Units Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	17,622
Estimated payout percentage based on performance criteria	118.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 64.57
2017 Grant [Member] | Performance Shares Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	63,565
Estimated payout percentage based on performance criteria	155.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 84.82
2017 Grant [Member] | Performance Units Liability Awards [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	16,952
Estimated payout percentage based on performance criteria	155.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 84.82