Condensed Consolidated Balance Sheets (Unaudited) Statement - USD ($) shares in Thousands, $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Fixed-maturities available for sale—at fair value, net of allowance for credit losses of $2,290 as of September 30, 2020 (amortized cost of $5,338,536 and $4,549,534)	$ 5,628,992	$ 4,688,911
Trading securities—at fair value (amortized cost of $262,131 and $297,505)	291,650	317,150
Equity securities—at fair value (cost of $92,638 and $125,311)	91,317	130,221
Short-term investments—at fair value (includes $33,121 and $25,561 of reinvested cash collateral held under securities lending agreements)	567,146	518,393
Other invested assets—at fair value	5,472	4,072
Investments, Total	6,584,577	5,658,747
Cash	82,020	92,729
Restricted cash	4,424	3,545
Accounts and notes receivable	145,164	93,630
Goodwill and other acquired intangible assets, net (Note 7)	25,268	28,187
Prepaid reinsurance premium	295,062	363,856
Other assets (Note 9)	640,830	567,619
Assets, Total	7,777,345	6,808,313
Liabilities and Stockholders’ Equity
Unearned premiums	501,787	626,822
Reserve for losses and loss adjustment expense (Note 11)	825,792	404,765
Senior notes (Note 12)	1,404,759	887,110
FHLB advances (Note 12)	141,058	134,875
Reinsurance funds withheld	318,773	291,829
Other Liabilities	462,797	414,189
Total liabilities	3,654,966	2,759,590
Stockholders’ equity
Common stock: par value $0.001 per share; 485,000 shares authorized at September 30, 2020 and December 31, 2019; 210,061 and 219,123 shares issued at September 30, 2020 and December 31, 2019, respectively; 191,556 and 201,164 shares outstanding at September 30, 2020 and December 31, 2019, respectively	210	219
Treasury stock, at cost: 18,505 and 17,959 shares at September 30, 2020 and December 31, 2019, respectively	(909,745)	(901,657)
Additional paid-in capital	2,238,869	2,449,884
Retained earnings	2,561,076	2,389,789
Accumulated other comprehensive income (loss) (Note 15)	231,969	110,488
Total stockholders’ equity	4,122,379	4,048,723
Total liabilities and stockholders’ equity	7,777,345	6,808,313
Equity Securities, FV-NI, Cost	92,638	125,311
Debt Securities, Trading, Amortized Cost	262,131	297,505
Fixed-maturities available for sale—at amortized cost	5,338,536	$ 4,549,534
Ending balance	$ (2,290)
Common Stock, Par or Stated Value Per Share	$ 0.001	$ 0.001
Common Stock, Shares Authorized	485,000	485,000
Common Stock, Shares, Issued	210,061	219,123
Common Stock, Shares, Outstanding	191,556	201,164
Treasury Stock, Shares	18,505	17,959
Reinvested Cash Collateral Held Under Securities Lending Agreements	$ 33,121	$ 25,561