Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net income	$ 111,069	$ 66,598
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on the sale of investments, net	(197)	(655)
Depreciation and amortization	897	1,001
Stock-based compensation expense	3,605	4,619
Amortization of premium on investment securities	3,287	2,983
Deferred income tax provision	9,882	18,042
Change in:
Accrued investment income	(1,576)	(703)
Accounts receivable	(2,238)	(1,887)
Deferred policy acquisition costs	(209)	(93)
Prepaid federal income tax	100,863	615
Other assets	(4,619)	(975)
Reserve for losses and LAE	3,116	1,326
Unearned premium reserve	12,667	1,646
Other accrued liabilities	(14,679)	(14,629)
Net cash provided by operating activities	221,868	77,888
Investing Activities
Net change in short-term investments	(68,068)	19,968
Purchase of investments available for sale	(266,847)	(200,795)
Proceeds from maturity of investments available for sale	16,601	18,206
Proceeds from sales of investments available for sale	102,458	60,129
Purchase of property and equipment	(508)	(1,087)
Net cash used in investing activities	(216,364)	(103,579)
Financing Activities
Credit facility borrowings	15,000	25,000
Treasury stock acquired	(31,070)	(7,127)
Net cash (used in) provided by financing activities	(16,070)	17,873
Net decrease in cash	(10,566)	(7,818)
Cash at beginning of year	43,524	27,531
Cash at end of period	32,958	19,713
Supplemental Disclosure of Cash Flow Information
Income tax payments	0	(1,200)
Interest payments	$ (2,324)	$ (701)