Statutory Information - Statutory financial information of insurance subsidiaries (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statutory Capital [Abstract]
Statutory net income (loss)	$ 65,201	$ 305,857	$ 375,484
Statutory policyholders' surplus	1,339,509	1,619,069	1,683,058
Contingency reserve	$ 3,585,864	$ 3,021,055	$ 2,442,996