The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Name:	us-gaap_RetainedEarningsAccumulatedDeficit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Accounting Developments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Jan. 01, 2020
New Accounting Pronouncements or Change in Accounting Principle
Retained Earnings	$ (11,754.8)	$ (11,269.6)
Accounting Standards Update 2016-13 \| Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle
Retained Earnings			$ 18.9