Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 11,961	$ 30,639
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Tax Effect Of Regulatory Treatment Of Utility Plant Differences	$ (2,402)	$ (2,080)
Tax Effect Of Regulatory Treatment Of Utility Plant Differences, Percent	(4.20%)	(1.40%)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	$ 1,227	$ 1,659
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	2.10%	1.10%
Income Tax Reconciliation, Nondeductible Expense, Acquisition Costs, Amount	$ 0	$ (1,824)
Income Tax Reconciliation, Nondeductible Expense, Acquisition Costs, Percent	0.00%	(1.20%)
Income Tax Reconciliation Settlement of Share Based Compensation Amount	$ 165	$ 612
Income Tax Reconciliation Settlement of Share Based Compensation Percent	0.30%	0.40%
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	$ (2,419)	$ 1,011
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent	(4.20%)	0.70%
Income tax expense	$ 8,532	$ 30,017
Effective Income Tax Rate Reconciliation, Percent	15.00%	20.60%