Employee Benefits (Retirement Plans And Other Postretirement Benefits) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,801	$ 2,129	$ 8,316	$ 6,388	$ 10,446	$ 8,388
Interest cost	3,214	3,264	9,659	9,794	12,924	13,053
Expected return on plan assets	(5,176)	(4,797)	(15,806)	(14,392)	(20,603)	(19,112)
Amortization of net (gain) loss	2,214	2,114	6,414	6,341	8,527	8,175
Amortization of prior service benefit	(875)	(877)	(2,630)	(2,630)	(3,506)	(3,506)
Net periodic benefit cost (benefit)	2,178	1,833	5,953	5,501	7,788	6,998
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	696	559	2,096	1,677	2,655	2,267
Interest cost	559	680	1,689	2,042	2,370	2,593
Expected return on plan assets	(602)	(477)	(1,827)	(1,430)	(2,304)	(1,893)
Amortization of net (gain) loss	(574)	(419)	(1,624)	(1,258)	(2,044)	(1,659)
Amortization of prior service benefit	(1,538)	(1,537)	(4,613)	(4,613)	(6,151)	(6,151)
Net periodic benefit cost (benefit)	$ (1,459)	$ (1,194)	$ (4,279)	$ (3,582)	$ (5,474)	$ (4,843)