Accumulated Other Comprehensive Income (Loss) Changes in AOCI, net of tax (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	$ (77,202)
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings	0	$ 5,230	$ 0
Accumulated other comprehensive income (loss), net of tax	(84,149)	(77,202)
Subsidiaries [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	(190,884)
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings	0	(27,333)	0
Accumulated other comprehensive income (loss), net of tax	(188,477)	(190,884)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	(77,202)	(24,282)	(33,712)
Other comprehensive income (loss) before reclassifications	(7,337)	(48,870)	10,251
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	390	1,180	(821)
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings		(5,230)
Net current-period other comprehensive income (loss)	(6,947)	(52,920)	9,430
Accumulated other comprehensive income (loss), net of tax	(84,149)	(77,202)	(24,282)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] \| Subsidiaries [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	(185,130)	(121,867)	(140,155)
Other comprehensive income (loss) before reclassifications	(8,096)	(48,802)	10,200
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	10,118	11,772	8,088
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings		(26,233)
Net current-period other comprehensive income (loss)	2,022	(63,263)	18,288
Accumulated other comprehensive income (loss), net of tax	(183,108)	(185,130)	(121,867)
Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	(77,202)	(24,282)	(33,712)
Other comprehensive income (loss) before reclassifications	(7,337)	(48,870)	10,251
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	390	1,180	(821)
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings		(5,230)
Net current-period other comprehensive income (loss)	(6,947)	(52,920)	9,430
Accumulated other comprehensive income (loss), net of tax	(84,149)	(77,202)	(24,282)
Comprehensive Income [Member] \| Subsidiaries [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	(190,884)	(126,906)	(145,511)
Other comprehensive income (loss) before reclassifications	(8,096)	(48,802)	10,200
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	10,503	12,157	8,405
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings		(27,333)
Net current-period other comprehensive income (loss)	2,407	(63,978)	18,605
Accumulated other comprehensive income (loss), net of tax	(188,477)	(190,884)	(126,906)
Interest Rate Swap [Member] \| Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] \| Subsidiaries [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax	(5,754)	(5,039)	(5,356)
Other comprehensive income (loss) before reclassifications		0	0
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	385	385	317
Other Comprehensive (Income) Loss, Reclassification of Stranded Taxes to Retained Earnings		(1,100)
Net current-period other comprehensive income (loss)	385	(715)	317
Accumulated other comprehensive income (loss), net of tax	$ (5,369)	$ (5,754)	$ (5,039)

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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