Schedule II Financial Information of Registrant Parent Company Statement of Cash Flows (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net cash provided by (used in) operating activities (1)		$ 694,431	$ 677,786	$ 360,575
Cash flows from investing activities:
Proceeds from sales of Fixed-maturity investments available-for-sale		986,647	728,584	888,219
Proceeds from sales of Trading securities		130,537	58,317	194,784
Proceeds from sales of Equity securities		69,779	95,697	38,318
Proceeds from redemptions of Fixed-maturity investments available for sale		464,777	457,595	463,548
Proceeds from redemptions of Trading securities		37,684	54,329	79,296
Purchases of Fixed-maturity investments available for sale		(1,913,703)	(1,875,069)	(1,947,916)
Sales, redemptions and (purchases) of Short-term investments, net		8,017	(108,325)	324,258
Sales, redemptions and (purchases) of Other assets, net		739	(2,590)	(882)
Net cash provided by (used in) investing activities		(302,049)	(689,414)	(201,492)
Cash flows from financing activities:
Dividends paid		(2,061)	(2,140)	(2,154)
Issuance of senior notes, net		442,439	0	442,163
Repayments and repurchases of senior notes		(610,763)	0	(593,527)
Proceeds from termination of capped calls		0	0	4,208
Issuance of common stock		2,416	1,385	7,132
Repurchases of common shares		(300,201)	(50,053)	(6)
Proceeds from (Payments for) Other Financing Activities		(989)	(1,510)	(1,993)
Net cash provided by (used in) financing activities		(403,106)	22,386	(125,084)
Effect of exchange rate changes on cash and restricted cash		(4)	0	431
Increase (decrease) in cash and restricted cash		(10,728)	10,758	34,430
Cash and restricted cash, beginning of period		107,002	96,244	61,814
Cash and restricted cash, end of period		96,274	107,002	96,244
Parent Company
Cash flows from operating activities:
Net cash provided by (used in) operating activities (1)	[1]	143,664	254,698	(23,654)
Cash flows from investing activities:
Proceeds from sales of Fixed-maturity investments available-for-sale		296,171	6,779	58,007
Proceeds from sales of Trading securities		56,787	0	0
Proceeds from sales of Equity securities		16,916	0	0
Proceeds from redemptions of Fixed-maturity investments available for sale		149,767	12,391	60,414
Proceeds from redemptions of Trading securities		114	0	0
Purchases of Fixed-maturity investments available for sale		(293,284)	(37,552)	(134,456)
Sales, redemptions and (purchases) of Short-term investments, net		157,045	(131,164)	210,529
Sales, redemptions and (purchases) of Other assets, net		(6,958)	(3,317)	(1,107)
Capital distributions from subsidiaries		6,000	0	924
Capital contributions to subsidiaries		(65,879)	(30,338)	(21,643)
(Issuance) repayment of note receivable from affiliate (Note B)		0	0	(44)
Net cash provided by (used in) investing activities		316,679	(183,201)	172,624
Cash flows from financing activities:
Dividends paid		(2,061)	(2,140)	(2,154)
Issuance of senior notes, net		442,439	0	442,163
Repayments and repurchases of senior notes		(610,763)	0	(593,527)
Proceeds from termination of capped calls		0	0	4,208
Issuance of common stock		2,416	1,385	7,132
Repurchases of common shares		(300,201)	(50,053)	(6)
Proceeds from (Payments for) Other Financing Activities		(989)	(1,510)	(1,993)
Net cash provided by (used in) financing activities		(469,159)	(52,318)	(144,177)
Effect of exchange rate changes on cash and restricted cash		(2)	0	0
Increase (decrease) in cash and restricted cash		(8,818)	19,179	4,793
Cash and restricted cash, beginning of period		32,352	13,173	8,380
Cash and restricted cash, end of period		23,534	32,352	13,173
Cash Distributions Received From Consolidated Subsidiaries		26,600	55,400	24,300
Dividends Received From Consolidated Subsidiaries		$ 362,400	$ 394,600	$ 197,300

[1] Includes cash distributions received from subsidiaries of $26.6 million, $55.4 million and $24.3 million in 2019, 2018 and 2017, respectively.