Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating Activities
Net income	$ 47,951	$ 34,838
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on the sale of investments, net	(471)	(649)
Depreciation and amortization	1,000	734
Stock-based compensation expense	3,782	3,261
Amortization of premium on investment securities	2,680	2,360
Deferred income tax provision	15,245	14,280
Excess tax benefits from stock-based compensation	(1,005)	(2,280)
Change in:
Accrued investment income	(663)	(492)
Accounts receivable	(563)	(1,151)
Deferred policy acquisition costs	(157)	(255)
Prepaid federal income tax	(110)	(4,000)
Other assets	539	(1,584)
Reserve for losses and LAE	2,710	1,638
Unearned premium reserve	6,063	7,219
Accrued liabilities	(9,509)	(6,739)
Net cash provided by operating activities	67,492	47,180
Investing Activities
Net change in short-term investments	2,508	98,766
Purchase of investments available for sale	(146,316)	(220,284)
Proceeds from maturity of investments available for sale	1,798	5,525
Proceeds from sales of investments available for sale	82,167	71,077
Purchase of property and equipment, net	(1,211)	(1,527)
Net cash used in investing activities	(61,054)	(46,443)
Financing Activities
Treasury stock acquired	(3,843)	(5,023)
Excess tax benefits from stock-based compensation	1,005	2,280
Payment of offering costs	0	(537)
Other financing activities	0	34
Net cash used in financing activities	(2,838)	(3,246)
Net increase (decrease) in cash	3,600	(2,509)
Cash at beginning of year	24,606	24,411
Cash at end of period	28,206	21,902
Supplemental Disclosure of Cash Flow Information
Income tax payments	$ (1,800)	$ 0