Unaudited Interim Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total Equity
Beginning Balance at Dec. 31, 2018		$ 2,500	$ 1,146,592	$ 1,612,435	$ (28,296)	$ 2,733,231
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Contributed (distributed) capital-parent/child asset transfers			(4)			(4)
Comprehensive income (loss):
Net income (loss)	$ 87,788			87,788		87,788
Other comprehensive income (loss), net of tax	132,501				132,501	132,501
Total comprehensive income (loss)						220,289
Ending Balance at Mar. 31, 2019		2,500	1,146,588	1,699,109	104,205	2,952,402
Beginning Balance at Dec. 31, 2019		2,500	1,153,632	1,577,453	281,442	3,015,027
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Contributed (distributed) capital-parent/child asset transfers			0	0		0
Comprehensive income (loss):
Net income (loss)	97,612			97,612		97,612
Other comprehensive income (loss), net of tax	$ (126,381)				(126,381)	(126,381)
Total comprehensive income (loss)						(28,769)
Ending Balance at Mar. 31, 2020		$ 2,500	$ 1,153,632	$ 1,673,313	$ 155,061	$ 2,984,506