Schedule II Financial Information of Registrant Parent Company Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Assets
Fixed-maturities available for sale—at fair value (amortized cost of $429,999 and $320,746)		$ 4,688,911	$ 4,021,575
Trading securities—at fair value (amortized cost of $0 and $55,948)		317,150	469,071
Equity securities—at fair value (cost of $13,280 and $29,387)		130,221	130,565
Short-term investments—at fair value		518,393	528,403
Other invested assets—at fair value		4,072	3,415
Total investments		5,658,747	5,153,029
Cash		92,729	95,393
Investment in subsidiaries, at equity in net assets (Note C)		4,200,000
Accounts and notes receivable		93,630	78,652
Federal income taxes recoverable, net—current	[1]	0	44,506
Other assets (Note C)		567,619	367,700
Total assets		6,808,313	6,314,652
Liabilities and Stockholders’ Equity
Senior notes		887,110	1,030,348
Other liabilities		414,189	251,127
Total liabilities		2,759,590	2,825,937
Common stock: par value $.001 per share; 485,000 shares authorized at December 31, 2019 and 2018; 219,123 and 231,132 shares issued at December 31, 2019 and 2018, respectively; 201,164 and 213,473 shares outstanding at December 31, 2019 and 2018, respectively		219	231
Treasury stock, at cost: 17,959 and 17,660 shares at December 31, 2019 and 2018, respectively		(901,657)	(894,870)
Additional paid-in capital		2,449,884	2,724,733
Retained earnings		2,389,789	1,719,541
Accumulated other comprehensive income (loss)		110,488	(60,920)
Total common stockholders’ equity		4,048,723	3,488,715
Total liabilities and stockholders’ equity		6,808,313	6,314,652
Parent Company
Assets
Fixed-maturities available for sale—at fair value (amortized cost of $429,999 and $320,746)		430,442	321,401
Trading securities—at fair value (amortized cost of $0 and $55,948)		0	56,011
Equity securities—at fair value (cost of $13,280 and $29,387)		13,381	29,375
Short-term investments—at fair value		162,363	238,185
Other invested assets—at fair value		1,500	0
Total investments		607,686	644,972
Cash		23,534	32,352
Investment in subsidiaries, at equity in net assets (Note C)		4,413,065	3,927,268
Accounts and notes receivable		100,775	101,072
Federal income taxes recoverable, net—current		0	49,381
Other assets (Note C)		113,917	58,993
Total assets		5,258,977	4,814,038
Liabilities and Stockholders’ Equity
Senior notes		887,110	1,030,348
Federal income taxes—deferred (Note A)		253,739	243,341
Other liabilities		69,405	51,634
Total liabilities		1,210,254	1,325,323
Common stock: par value $.001 per share; 485,000 shares authorized at December 31, 2019 and 2018; 219,123 and 231,132 shares issued at December 31, 2019 and 2018, respectively; 201,164 and 213,473 shares outstanding at December 31, 2019 and 2018, respectively		219	231
Treasury stock, at cost: 17,959 and 17,660 shares at December 31, 2019 and 2018, respectively		(901,657)	(894,870)
Additional paid-in capital		2,449,884	2,724,733
Retained earnings		2,389,789	1,719,541
Accumulated other comprehensive income (loss)		110,488	(60,920)
Total common stockholders’ equity		4,048,723	3,488,715
Total liabilities and stockholders’ equity		$ 5,258,977	$ 4,814,038
Balance Sheet Parentheticals [Abstract]
Common Stock, Par or Stated Value Per Share		$ 0.001	$ 0.001
Common Stock, Shares Authorized		485,000,000	485,000,000
Common Stock, Shares, Issued		219,123,000	231,132,000
Common Stock, Shares, Outstanding		201,164,000	213,473,000
Treasury Stock, Shares		17,959,000	17,660,000

[1] During the year ended December 31, 2019, current federal income tax receivable was reduced by our receipt of the remaining $57.2 million refund from amounts on deposit with the IRS related to the settlement of the IRS Matter.