Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	$ 155,800	$ 217,778
Cash Flows from Investing Activities:
Proceeds from Sales of Fixed-Maturity Investments Available for sale	533,019	435,709
Proceeds from Sales of Trading Securities	9,936	70,083
Proceeds from Sales of Equity Securities	59,339	33,278
Proceeds from Redemption of Fixed-Maturity Investments Available for sale	151,559	79,915
Proceeds from Redemptions of Trading securities	16,427	23,293
Purchases of Fixed-Maturity Investments Available for sale	(619,024)	(275,531)
Purchases of Equity Securities	(60,309)	(19,767)
Sales, Redemptions and (Purchases) of Short-term Investments, Net	(72,220)	(526,013)
Sales, Redemptions and (Purchases) of Other assets and other invested assets, net	2,347	349
Proceeds from sale of a subsidiary, net of cash sold	15,869	0
Purchases of property and equipment, net	(4,950)	(6,659)
Net cash provided by (used in) investing activities	31,993	(185,343)
Cash Flows from Financing Activities:
Dividends and dividend equivalents paid	(25,138)	(534)
Issuance of common stock	1,447	363
Repurchases of common shares	(226,305)	(31,774)
Credit facility commitment fees paid	(237)	(234)
Change in secured borrowings, net (with terms 3 months or less)	(2,854)	21,534
Proceeds from secured borrowings (with terms greater than 3 months)	59,995	6,000
Payments of secured borrowings (with terms greater than 3 months)	(29,011)	(7,000)
Repayments of other borrowings	(39)	(38)
Net cash provided by (used in) financing activities	(222,142)	(11,683)
Increase (decrease) in cash and restricted cash	(34,349)	20,752
Cash and restricted cash, beginning of period	96,274	107,002
Cash and restricted cash, end of period	$ 61,925	$ 127,754