Summary of Significant Accounting Policies Summary of Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
Jun. 30, 2020	Jun. 30, 2019
Adjustments to Additional Paid in Capital, Other		$ 0
Internal Reorganization [Member]
Adjustments to Additional Paid in Capital, Other	$ 40	$ 76

Amount of other increase (decrease) in additional paid in capital (APIC).

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration