Pension Plan and Employee Benefits - 401 (K) Plans (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense		$ 2,512	$ 2,356	$ 7,391	$ 7,509
Percent of employees' gross pay, one time benefit (up to)	30.00%	30.00%		30.00%
401(k) Plan expense, additional cost	$ 200
Other Subsidiaries
Defined Contribution Plan Disclosure [Line Items]
401(k) Plan expense		$ 1,185	$ 996	$ 3,511	$ 3,491