Basis of Presentation and Accounting Policies (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase to retirement obligations and other liabilities	$ 497,724	$ 517,566	$ 543,221	$ 529,946
Increase to retained earnings	3,677,117	3,670,543	3,640,227	3,610,470
Increase to accumulated other comprehensive loss	$ (600,143)	(609,625)	$ (635,292)	$ (653,916)
Foreign Currency Transactions
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase to retirement obligations and other liabilities		1,500
Increase to retained earnings		14,000
Increase to accumulated other comprehensive loss		$ (15,500)

- Definition

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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