Condensed Financial Information - Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$ 95,329us-gaap_NetIncomeLoss	$ 63,466us-gaap_NetIncomeLoss	$ 63,762us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash provided by (used in) operations:
Call premium on redemption of Senior Notes		17,895
Other	29,039	31,987	36,503
Net cash provided by (used in) operating activities	222,492	136,875	96,739
Fixed maturities, available-for-sale
Sales	362,136	648,335	1,319,404
Purchases	(864,902)	(899,930)	(1,711,080)
Equity securities
Sales	54,900	72,113	39,503
Purchases	(83,845)	(89,288)	(37,587)
Net increase in short-term investments	117,740	(142,214)	(31,568)
Net cash provided by (used in) investing activities	(219,470)	(229,859)	(179,839)
Financing activities:
Net Proceeds from Debt Offering		263,278us-gaap_ProceedsFromIssuanceOfDebt
Redemption of 7.0% Senior Notes Due May 1, 2016		(132,437)us-gaap_EarlyRepaymentOfSeniorDebt
Proceeds of stock issued from employee stock purchase plan	1,067us-gaap_ProceedsFromStockPlans	821us-gaap_ProceedsFromStockPlans	672us-gaap_ProceedsFromStockPlans
Proceeds of stock issued from exercise of stock options	153	2,495	404
Net cash provided by (used in) financing activities	1,220	134,157	1,076
Cash at beginning of year	86,509us-gaap_Cash	45,336us-gaap_Cash	127,360us-gaap_Cash
Cash at end of period	90,751us-gaap_Cash	86,509us-gaap_Cash	45,336us-gaap_Cash
Parent Company
Operating activities:
Net income	95,329	63,466	63,762
Adjustments to reconcile net income to net cash provided by (used in) operations:
Equity in undistributed net income of wholly-owned subsidiaries	(105,379)	(81,971)	(70,036)
Dividends received from subsidiaries			15,000
Call premium on redemption of Senior Notes		17,895
Other	9,211	2,098	(3,265)
Net cash provided by (used in) operating activities	(839)	1,488	5,461
Fixed maturities, available-for-sale
Sales	3,200	8,754	7,986
Purchases		(1,249)	(14,700)
Equity securities
Sales	0	0	0
Purchases	0	0	0
Net increase in short-term investments	(3,424)	(89,988)	(167)
Net cash provided by (used in) investing activities	(224)	(82,483)	(6,881)
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	0	0	0
Proceeds of stock issued from employee stock purchase plan	1,067	821	672
Proceeds of stock issued from exercise of stock options	153	2,495	404
Net cash provided by (used in) financing activities	1,220	84,157	1,076
Increase (decrease) in cash	157	3,162	(344)
Cash at beginning of year	6,143	2,981	3,325
Cash at end of period	$ 6,300	$ 6,143	$ 2,981

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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