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Income Taxes Income Taxes - NPC (Details)
3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Schedule of Effective Income Tax Rate Reconciliation [Line Items]    
Federal statutory income tax rate 21.00% 21.00%
Effective Income Tax Rate Reconciliation Regulatory Differences 8.00% 3.00%
Other, net (1.00%) (2.00%)
Effective income tax rate 36.00% 30.00%