Retirement, Other Postretirement Benefits, And Defined Contribution Plans (Investments Held For Qualified Pension And Other Postretirement Plans Measured At Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	$ 6,122,808	$ 5,208,228
Cash	1,508	929
Other pending transactions	5,179	8,869
Less: Other postretirement assets included in total investments	(58,179)	(46,824)
Total fair value of qualified pension assets	6,071,316	5,171,202
Qualified Pension Plans [Member] | Interest Bearing Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments		3,610
Qualified Pension Plans [Member] | Preferred [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	11,461	6,423
Qualified Pension Plans [Member] | Common Stock [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	663,957	745,754
Qualified Pension Plans [Member] | Common Collective Trusts [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	3,198,799	2,072,743
Qualified Pension Plans [Member] | 103-12 Investment Entities [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments		335,818
Qualified Pension Plans [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	638,832	370,681
Qualified Pension Plans [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	619,735	630,726
Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	125,174	258,879
Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	764,251	640,836
Qualified Pension Plans [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	62,605	105,647
Qualified Pension Plans [Member] | Insurance Company General Account (Unallocated Contracts) [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	37,994	37,111
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	600,154	549,732
Other pending transactions	994	104
Plus: Other postretirement assets included in the investments of the qualified pension trust	58,179	46,824
Total fair value of qualified pension assets	659,327	596,660	$ 579,069
Other Postretirement Benefit Plan [Member] | Common Collective Trusts [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	300,139	368,704
Other Postretirement Benefit Plan [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	158,392	73,729
Other Postretirement Benefit Plan [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	92,869	58,787
Other Postretirement Benefit Plan [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	3,127	3,123
Other Postretirement Benefit Plan [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	45,627	45,389
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	846,372	1,046,403
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Interest Bearing Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments		0
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Preferred [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	11,461	6,423
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Common Stock [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	663,923	745,715
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Common Collective Trusts [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | 103-12 Investment Entities [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	136
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	125,174	258,879
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	45,768	35,216
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	46	34
Fair Value Inputs Level 1 [Member] | Qualified Pension Plans [Member] | Insurance Company General Account (Unallocated Contracts) [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	84,729	33,755
Fair Value Inputs Level 1 [Member] | Other Postretirement Benefit Plan [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	81,602	30,632
Fair Value Inputs Level 1 [Member] | Other Postretirement Benefit Plan [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 1 [Member] | Other Postretirement Benefit Plan [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	3,127	3,123
Fair Value Inputs Level 1 [Member] | Other Postretirement Benefit Plan [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	1,361,889	1,150,339
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Interest Bearing Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments		3,610
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Preferred [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Common Stock [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	34	39
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Common Collective Trusts [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | 103-12 Investment Entities [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	638,832	370,545
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	619,735	630,726
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	2,735	2,695
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	62,559	105,613
Fair Value Inputs Level 2 [Member] | Qualified Pension Plans [Member] | Insurance Company General Account (Unallocated Contracts) [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	37,994	37,111
Fair Value Inputs Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	215,286	147,273
Fair Value Inputs Level 2 [Member] | Other Postretirement Benefit Plan [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	76,790	43,097
Fair Value Inputs Level 2 [Member] | Other Postretirement Benefit Plan [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	92,869	58,787
Fair Value Inputs Level 2 [Member] | Other Postretirement Benefit Plan [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 2 [Member] | Other Postretirement Benefit Plan [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	45,627	45,389
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Interest Bearing Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments		0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Preferred [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Common Stock [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Common Collective Trusts [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | 103-12 Investment Entities [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Qualified Pension Plans [Member] | Insurance Company General Account (Unallocated Contracts) [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Other Postretirement Benefit Plan [Member] | U.S. Government securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Other Postretirement Benefit Plan [Member] | Corporate Debt Securities [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Other Postretirement Benefit Plan [Member] | Registered Investment Companies [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	0	0
Fair Value Inputs Level 3 [Member] | Other Postretirement Benefit Plan [Member] | Other [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Investments	$ 0	$ 0