CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 512,351	$ 328,447
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	45,267	48,882
Deferred tax expense	145,397	165,250
Net realized investment losses	1,112	227
Loss on debt extinguishment	0	65
Change in certain assets and liabilities:
Accrued investment income	694	1,145
Reinsurance recoverable on loss reserves	15,193	4,615
Reinsurance recoverable on paid losses	761	326
Premium receivable	2,405	(1,546)
Deferred insurance policy acquisition costs	176	(1,265)
Profit commission receivable	(9,098)	(3,899)
Loss reserves	(264,589)	(333,662)
Unearned premiums	14,680	41,079
Return premium accrual	(18,600)	(18,000)
Current income taxes	(75,393)	34,974
Other, net	13,191	(10,282)
Net cash provided by operating activities	383,547	256,356
Cash flows from investing activities:
Purchases of investments	(1,074,849)	(775,043)
Proceeds from sales of investments	338,939	233,198
Proceeds from maturity of fixed income securities	594,679	547,699
Net increase in payable for securities	43,679	3,738
Additions to property and equipment	(10,659)	(12,121)
Net cash used in investing activities	(108,211)	(2,529)
Cash flows from financing activities:
Proceeds from revolving credit facility	0	150,000
Repayment of revolving credit facility	0	(150,000)
Purchase or repayment of convertible senior notes	0	(145,620)
Payment of original issue discount - convertible senior notes	0	(4,504)
Repurchase of common stock	(100,059)	0
Payment of debt issuance costs	0	(1,630)
Payment of withholding taxes related to share-based compensation net share settlement	(8,131)	(6,782)
Net cash used in financing activities	(108,190)	(158,536)
Net increase in cash and cash equivalents	167,146	95,291
Cash and cash equivalents at beginning of period	99,851	155,410
Cash and cash equivalents at end of period	$ 266,997	$ 250,701