Benefit Plans (Fair Values Of Nonvested Performance Shares And Performance Units) (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	203,188
Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	57,761
2018 Grant [Member] | Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	70,483
Estimated payout percentage based on performance criteria	85.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 35.91
2018 Grant [Member] | Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	19,196
Estimated payout percentage based on performance criteria	85.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 35.91
2017 Grant [Member] | Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	65,350
Estimated payout percentage based on performance criteria	85.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 35.91
2017 Grant [Member] | Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	18,062
Estimated payout percentage based on performance criteria	85.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 35.91
2016 Grant [Member] | Performance Shares [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	67,355
Estimated payout percentage based on performance criteria	143.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 60.42
2016 Grant [Member] | Performance Units [Member]
Defined Benefit Plan Disclosure [Line Items]
Nonvested, December 31 (in shares/awards)	20,503
Estimated payout percentage based on performance criteria	143.00%
Fair values of each nonvested award (in dollars per share) | $ / shares	$ 60.42