CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 670,097	$ 355,761	$ 342,517
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and other amortization	58,215	64,430	61,342
Deferred tax expense	186,572	355,044	162,356
Net realized investment losses (gains)	1,353	(231)	(8,921)
Loss on debt extinguishment	0	65	90,531
Change in certain assets and liabilities:
Accrued investment income	(1,941)	(1,987)	(3,849)
Reinsurance recoverable on loss reserves	15,146	2,019	(6,006)
Reinsurance recoverable on paid losses	924	1,092	(1,645)
Premiums receivable	(1,045)	(1,653)	(3,923)
Deferred insurance policy acquisition costs	953	(1,082)	(2,518)
Profit commission receivable	(5,479)	(2,844)	(747)
Loss reserves	(311,616)	(453,178)	(454,589)
Unearned premiums	17,051	63,197	49,764
Return premium accrual	(22,900)	(25,400)	(18,800)
Current income taxes	(77,551)	51,296	4,941
Other, net	14,738	128	14,307
Net cash provided by operating activities	544,517	406,657	224,760
Cash flows from investing activities:
Purchases of investments	(1,459,473)	(1,293,695)	(1,363,583)
Proceeds from sales of investments	370,449	246,908	733,299
Proceeds from maturity of fixed income securities	785,175	759,212	547,444
Net increase in payables for securities	307	0	0
Additions to property and equipment	(14,238)	(16,066)	(10,552)
Net cash used in investing activities	(317,780)	(303,641)	(93,392)
Cash flows from financing activities:
Proceeds from revolving credit facility	0	150,000	0
Repayment of revolving credit facility	0	(150,000)	0
Proceeds from issuance of long-term debt	0	0	573,094
Purchase or repayment of convertible senior notes	0	(145,620)	(363,778)
Payment of original issue discount - convertible senior notes	0	(4,504)	(11,250)
Purchase of convertible junior subordinated debentures	0	0	(100,860)
Payment of original issue discount-convertible junior subordinated debentures	0	0	(41,540)
Cash portion of loss on debt extinguishment	0	0	(59,460)
Repurchase of common stock	(163,419)	0	(147,127)
Payment of debt issuance costs	0	(1,630)	(1,127)
Payment of withholding taxes related to share-based compensation net share settlement	(8,131)	(6,821)	(5,030)
Net cash used in financing activities	(171,550)	(158,575)	(157,078)
Net increase (decrease) in cash and cash equivalents and restricted cash and cash equivalents	55,187	(55,559)	(25,710)
Cash and cash equivalents and restricted cash and cash equivalents at beginning of year	99,851	155,410	181,120
Cash and cash equivalents and restricted cash and cash equivalents at end of year	$ 155,038	$ 99,851	$ 155,410