Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Activities
Net income	$ 157,331	$ 88,497	$ 65,413
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on the sale of investments, net	(2,554)	(925)	(116)
Depreciation and amortization	3,219	2,464	2,252
Amortization of discount on payments due under Asset Purchase Agreement	0	51	108
Stock-based compensation expense	13,633	12,520	3,597
Amortization of premium on investment securities	10,004	6,840	3,129
Deferred income tax provision	52,157	44,614	(8,267)
Excess tax benefits from stock-based compensation	(2,420)	(1,809)	0
Change in:
Accrued investment income	(2,020)	(3,770)	(687)
Accounts receivable	(2,828)	(3,803)	(5,112)
Deferred policy acquisition costs	(1,932)	(3,424)	(3,970)
Prepaid federal income tax	(59,739)	(51,673)	(8,000)
Other assets	(724)	78	(1,628)
Reserve for losses and LAE	9,333	5,357	1,571
Unearned premium reserve	44,097	53,549	62,829
Accounts payable and accrued expenses	6,582	5,138	7,889
Net cash provided by operating activities	224,139	153,704	119,008
Investing Activities
Net change in short-term investments	124,692	(196,609)	(6,982)
Purchase of investments available for sale	(798,891)	(699,324)	(136,094)
Proceeds from maturity of investments available for sale	8,613	27,382	12,400
Proceeds from sales of investments available for sale	449,834	144,744	36,582
Purchase of property and equipment, net	(4,960)	(3,893)	(2,666)
Net cash used in investing activities	(220,712)	(727,700)	(96,760)
Financing Activities
Issuance of common shares net of costs	(537)	126,441	438,403
Treasury stock acquired	(5,168)	(2,498)	(311)
Excess tax benefits from stock-based compensation	2,420	1,809	0
Payments under Asset Purchase Agreement	0	(5,000)	(5,000)
Other financing activities	53	0	0
Net cash (used in) provided by financing activities	(3,232)	120,752	433,092
Net increase (decrease) in cash	195	(453,244)	455,340
Cash at beginning of year	24,411	477,655	22,315
Cash at end of year	24,606	24,411	477,655
Supplemental Disclosure of Cash Flow Information
Income tax payments	(15,500)	(1,000)	(1,076)
Noncash Transactions
Issuance of management incentive shares (see Note 9)	$ 0	$ 416	$ 615