Condensed Financial Information of Registrant - Statements of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Statement of Income Captions [Line Items]
Net income (loss)		$ 364,189	$ (81,297)	$ (409,086)
Other comprehensive income (loss):
Other post-retirement benefits income (loss), net of tax		5,627	6,244	(4,324)
Total other comprehensive income (loss), net of tax		5,627	6,244	(4,324)
Comprehensive income (loss)		369,816	(75,053)	(413,410)
Parent Company
Condensed Statement of Income Captions [Line Items]
Net income (loss)		364,189	(81,297)	(409,086)
Other comprehensive income (loss):
Other post-retirement benefits income (loss), net of tax	[1]	5,627	6,244	(4,324)
Total other comprehensive income (loss), net of tax	[1]	5,627	6,244	(4,324)
Comprehensive income (loss)	[1]	$ 369,816	$ (75,053)	$ (413,410)

[1] Other comprehensive income (loss) relates to benefit plans at our subsidiaries.