Condensed Financial Information - Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:
Net income	$ 63,466	$ 63,762	$ 25,597
Adjustments to reconcile net income to net cash provided by (used in) operations:
Call premium on redemption of Senior Notes	17,895
Other	31,987	36,503	19,569
Net cash provided by (used in) operating activities	136,875	96,739	118,338
Fixed maturities, available-for-sale
Sales	648,335	1,319,404	666,976
Purchases	(899,930)	(1,711,080)	(803,568)
Equity securities
Sales	72,113	39,503	73,590
Net increase in short-term investments	(142,214)	(31,568)	30,384
Net cash provided by (used in) investing activities	(229,859)	(179,839)	66,006
Financing activities:
Net Proceeds from Debt Offering	263,278
Redemption of 7.0% Senior Notes Due May 1, 2016	(132,437)
Purchase of treasury stock			(90,866)
Proceeds of stock issued from employee stock purchase plan	821	672	945
Proceeds of stock issued from exercise of stock options	2,495	404	1,169
Net cash provided by (used in) financing activities	134,157	1,076	(88,752)
Cash at beginning of year	45,336	127,360	31,768
Cash at end of period	86,509	45,336	127,360
Parent Company
Operating activities:
Net income	63,466	63,762	25,597
Adjustments to reconcile net income to net cash provided by (used in) operations:
Equity in undistributed net income of wholly-owned subsidiaries	(81,971)	(70,036)	(32,524)
Dividends received from subsidiaries		15,000	45,000
Call premium on redemption of Senior Notes	17,895
Other	2,098	(3,265)	5,831
Net cash provided by (used in) operating activities	1,488	5,461	43,904
Fixed maturities, available-for-sale
Sales	8,754	7,986	45,716
Purchases	(1,249)	(14,700)	(9,253)
Equity securities
Sales
Purchases
Net increase in short-term investments	(89,988)	(167)	10,064
Net cash provided by (used in) investing activities	(82,483)	(6,881)	46,527
Financing activities:
Capital contribution to subsidiary	(50,000)
Net Proceeds from Debt Offering	263,278
Redemption of 7.0% Senior Notes Due May 1, 2016	(132,437)
Purchase of treasury stock			(90,866)
Proceeds of stock issued from employee stock purchase plan	821	672	945
Proceeds of stock issued from exercise of stock options	2,495	404	1,169
Net cash provided by (used in) financing activities	84,157	1,076	(88,752)
Increase (decrease) in cash	3,162	(344)	1,679
Cash at beginning of year	2,981	3,325	1,646
Cash at end of period	$ 6,143	$ 2,981	$ 3,325