Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating Activities
Net income	$ 66,598	$ 47,951
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on the sale of investments, net	(655)	(471)
Depreciation and amortization	1,001	1,000
Stock-based compensation expense	4,619	3,782
Amortization of premium on investment securities	2,983	2,680
Deferred income tax provision	18,042	15,245
Change in:
Accrued investment income	(703)	(663)
Accounts receivable	(1,887)	(563)
Deferred policy acquisition costs	(93)	(157)
Prepaid federal income tax	615	(110)
Other assets	(975)	539
Reserve for losses and LAE	1,326	2,710
Unearned premium reserve	1,646	6,063
Other accrued liabilities	(14,629)	(9,509)
Net cash provided by operating activities	77,888	68,497
Investing Activities
Net change in short-term investments	19,968	2,508
Purchase of investments available for sale	(200,795)	(146,316)
Proceeds from maturity of investments available for sale	18,206	1,798
Proceeds from sales of investments available for sale	60,129	82,167
Purchase of property and equipment	(1,087)	(1,211)
Net cash used in investing activities	(103,579)	(61,054)
Financing Activities
Revolving credit facility borrowings	25,000	0
Treasury stock acquired	(7,127)	(3,843)
Net cash provided by (used in) financing activities	17,873	(3,843)
Net (decrease) increase in cash	(7,818)	3,600
Cash at beginning of year	27,531	24,606
Cash at end of period	19,713	28,206
Supplemental Disclosure of Cash Flow Information
Income tax payments	(1,200)	(1,800)
Interest payments	$ (701)	$ 0