Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	$ 338,129	$ 300,822
Cash flows from investing activities:
Proceeds from Sales of Fixed-Maturity Investments Available-for-sale	568,351	348,082
Proceeds from Sales of Trading Securities	111,713	16,639
Proceeds from Sales of Equity Securities	39,818	82,701
Proceeds from Redemption of Fixed-Maturity Investments Available for sale	184,464	219,825
Proceeds from Redemptions of Trading securities	35,852	33,849
Purchases of Fixed-Maturity Investments Available-for-sale	(665,882)	(807,204)
Purchases of Equity Securities	(31,853)	(52,357)
Sales, Redemptions and (Purchases) of Short-term Investments, Net	(372,540)	(205,566)
Sales, Redemptions and (Purchases) of Other assets and other invested assets, net	490	293
Purchases of property and equipment, net	(15,207)	(12,328)
Acquisitions, net of cash acquired	0	(634)
Net cash provided by (used in) investing activities	(144,794)	(376,700)
Cash flows from financing activities:
Dividends paid	(1,053)	(1,073)
Issuance of senior notes, net	442,937	0
Repayments and repurchases of senior notes	(508,017)	0
Issuance of common stock	1,268	810
Repurchases of common shares	(188,817)	(50,053)
Credit facility commitment fees paid	(471)	(405)
Change in secured borrowings, net (with terms less than 3 months)	11,563	119,631
Proceeds from secured borrowings (with terms greater than 3 months)	36,000	15,544
Payments of secured borrowings (with terms greater than 3 months)	(14,550)	0
Repayments of other borrowings	(75)	(94)
Net cash provided by (used in) financing activities	(221,215)	84,360
Effect of exchange rate changes on cash and restricted cash	(4)	(1)
Increase (decrease) in cash and restricted cash	(27,884)	8,481
Cash and restricted cash, beginning of period	107,002	96,244
Cash and restricted cash, end of period	$ 79,118	$ 104,725