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

No definition available.

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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

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- Definition

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

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- Definition

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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- Definition

Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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Accumulated Other Comprehensive Loss, Net of Tax (Schedule of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	9 Months Ended			12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 2,886,515	$ 2,701,958	$ 2,527,012	$ 2,886,515	$ 2,701,958	$ 2,527,012
Adoption of ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from AOCI							$ 0
Other comprehensive (loss) income, net of tax	94,580	(39,121)	1,110	94,580	(39,121)	1,110
Ending Balance				3,207,770	2,886,515	2,701,958
Available For Sale and Transferred Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(27,947)	(15,476)		(27,947)	(15,476)
Other comprehensive income (loss) before reclassifications	88,647	(43,427)				(7,590)
Adoption of ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from AOCI							(4,881)
Amounts reclassified from accumulated other comprehensive loss	(22)	0				0
Other comprehensive (loss) income, net of tax	88,625	(43,427)				(7,590)
Ending Balance	17,251	(71,374)				(27,947)
Derivative Instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(15,016)	(17,068)		(15,016)	(17,068)
Other comprehensive income (loss) before reclassifications	(4,945)	208				181
Adoption of ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from AOCI							(2,513)
Amounts reclassified from accumulated other comprehensive loss	5,074	5,495				4,384
Other comprehensive (loss) income, net of tax	129	5,703				4,565
Ending Balance	(9,184)	(9,313)				(15,016)
Defined Benefit Pension and Postretirement Benefit Plans [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(48,568)	(44,449)		(48,568)	(44,449)
Other comprehensive income (loss) before reclassifications	1,622	(7,122)				98
Adoption of ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from AOCI							(8,254)
Amounts reclassified from accumulated other comprehensive loss	4,204	5,725		4,204	5,725	4,037
Other comprehensive (loss) income, net of tax	5,826	(1,397)				4,135
Ending Balance	(44,139)	(49,965)				(48,568)
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(130,652)	(91,531)	$ (76,993)	(130,652)	(91,531)	(76,993)
Other comprehensive income (loss) before reclassifications	85,324	(50,341)				(7,311)
Adoption of ASU No. 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220) - Reclassification of Certain Tax Effects from AOCI							$ (15,648)
Amounts reclassified from accumulated other comprehensive loss	9,256	11,220				8,421
Other comprehensive (loss) income, net of tax	94,580	(39,121)		94,580	(39,121)	1,110
Ending Balance	$ (36,072)	$ (130,652)		$ (36,072)	$ (130,652)	$ (91,531)