Retirement Benefit Plans (Fair Values of Pension Plan Assets) (Details) - Pension Benefits [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 752,138	$ 542,618
Cash And Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,574	8,643
Total Cash and Cash-Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,574	8,643
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69,401	116,881
Mutual Fund-Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34,652	31,701
Exchange Traded Fund (ETF)-Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,134
Total Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	107,187	148,582
Domestic And Foreign Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	88,174	80,819
Mutual Funds-Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	236,436	150,466
Total Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	324,610	231,285
Total Real Assets At Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	434,371	388,510
Common Trust Fund (Fixed Income) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	258,572	125,706
Common Trust Fund (Real Assets) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59,195	28,402
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	388,420	291,334
Level 1 [Member] | Cash And Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,574	8,643
Level 1 [Member] | Total Cash and Cash-Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,574	8,643
Level 1 [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	23,450	19,856
Level 1 [Member] | Mutual Fund-Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34,652	31,556
Level 1 [Member] | Exchange Traded Fund (ETF)-Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3,134
Level 1 [Member] | Total Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	61,236	51,412
Level 1 [Member] | Domestic And Foreign Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	88,174	80,813
Level 1 [Member] | Mutual Funds-Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	236,436	150,466
Level 1 [Member] | Total Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	324,610	231,279
Level 1 [Member] | Total Real Assets At Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	388,420	291,334
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45,951	97,031
Level 2 [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45,951	97,025
Level 2 [Member] | Total Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	45,951	97,025
Level 2 [Member] | Domestic And Foreign Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		6
Level 2 [Member] | Total Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		6
Level 2 [Member] | Total Real Assets At Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 45,951	97,031
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		145
Level 3 [Member] | Mutual Fund-Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		145
Level 3 [Member] | Total Fixed Income [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		145
Level 3 [Member] | Total Real Assets At Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 145