Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net income	$ 77,865	$ 70,462	$ 53,666
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	1,181	1,348	1,298
Net amortization of investments	16,247	16,424	15,243
Deferred income taxes	(2,249)	1,446	(1,412)
Net realized (gains) losses on investments	509	2,494	(697)
Net realized losses on disposal of assets	1	664
Share-based compensation	1,603	1,223	1,519
Changes in operating assets and liabilities:
Premiums receivable, net	2,359	(6,447)	(7,338)
Accrued interest receivable	325	(48)	(395)
Deferred policy acquisition costs	1,112	(763)	(478)
Amounts held by others	1,016	(27,847)	(1,082)
Other assets	1,631	(1,042)	(4,306)
Reserves for loss and loss adjustment expenses	24,743	30,431	73,045
Unearned premiums	(5,955)	(593)	4,280
Reinsurance balances	7,285	(5,878)	(10,326)
Amounts held for others and policyholder deposits	(17,066)	6,621	11,190
Accounts payable and other liabilities	3,605	4,364	6,477
Net cash provided by operating activities	114,212	92,859	140,684
Investing activities
Purchases of investments held-to-maturity	(102,830)	(178,010)	(223,028)
Purchases of investments available-for-sale	(216,466)	(135,915)	(149,956)
Purchases of short-term investments	(35,295)	(12,246)	(79,957)
Proceeds from maturities of investments held-to-maturity	177,159	160,834	112,100
Proceeds from sales and maturities of investments available-for-sale	115,552	78,637	72,535
Proceeds from sales and maturities of short-term investments	13,040	37,833	128,043
Purchases of property and equipment	(1,638)	(953)	(989)
Net cash (used in) provided by investing activities	(50,478)	(49,820)	(141,252)
Financing activities
Proceeds from stock option exercises	837	1,844	2,674
Tax benefit from share-based payments	995	2,203	2,841
Dividends to shareholders	(76,111)	(68,561)	(37,068)
Net cash used in financing activities	(74,279)	(64,514)	(31,553)
Change in cash and cash equivalents	(10,545)	(21,475)	(32,121)
Cash and cash equivalents at beginning of year	69,481	90,956	123,077
Cash and cash equivalents at end of year	58,936	69,481	90,956
Supplemental disclosure of cash flow information
Income taxes paid	$ 31,500	$ 23,851	$ 19,926