Schedule II - Condensed Financial Information of Registrant - Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating Activities:
Net Cash Provided by (Used in) Operating Activities	$ 3,815,227	$ 3,427,555	$ 2,886,505
Investing Activities:
Net (purchases) sales of short-term investments	467,249	165,272	(1,029,681)
Purchases of fixed assets	(51,672)	(41,394)	(39,872)
Other	125,405	(523,864)	(62,197)
Net cash used for investing activities	(3,102,055)	(2,139,732)	(3,043,226)
Financing Activities:
Purchases of common shares under share repurchase program	(585,823)	(1,234,294)	(83,472)
Proceeds from common shares issued, net	6,660	6,418	1,876
Proceeds from issuance of preferred shares, net	0	485,821	0
Redemption of preferred shares	0	(450,000)	0
Proceeds from borrowings	0	0	1,018,793
Preferred dividends paid	(40,736)	(48,280)	(41,612)
Net Cash Provided by (Used in) Financing Activities	(705,726)	(1,229,549)	521,278
Increase (decrease) in cash and restricted cash	(41,443)	24,227	386,846
Cash and restricted cash, beginning of year	1,314,771	1,290,544	903,698
Cash and restricted cash, end of year	1,273,328	1,314,771	1,290,544
Parent
Operating Activities:
Net Cash Provided by (Used in) Operating Activities	621,307	1,727,529	124,751
Investing Activities:
Net (purchases) sales of short-term investments	(4,838)	(1,866)	(130)
Capital contributed to subsidiaries	0	(487,161)	(988,975)
Purchases of fixed assets	(22)	(783)	(15)
Other	(1,462)	0	0
Net cash used for investing activities	(6,322)	(489,810)	(989,120)
Financing Activities:
Purchases of common shares under share repurchase program	(585,823)	(1,234,294)	(83,472)
Proceeds from common shares issued, net	6,660	6,418	1,876
Proceeds from issuance of preferred shares, net	0	485,821	0
Redemption of preferred shares	0	(450,000)	0
Proceeds from borrowings	0	0	988,393
Preferred dividends paid	(40,736)	(48,280)	(41,612)
Net Cash Provided by (Used in) Financing Activities	(619,899)	(1,240,335)	865,185
Increase (decrease) in cash and restricted cash	(4,914)	(2,616)	816
Cash and restricted cash, beginning of year	16,344	18,960	18,144
Cash and restricted cash, end of year	$ 11,430	$ 16,344	$ 18,960