Pension Plan and Employee Benefits - 401 (K) Plans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense	$ 1,898	$ 1,792	$ 5,154	$ 4,059
Other Subsidiaries
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense	$ 832	$ 821	$ 2,495	$ 1,752