SCHEDULE II-CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets
Fixed maturities (amortized cost, 2011-$421,250; 2010-$844,383)	$ 5,820,900				$ 7,455,238					$ 5,820,900	$ 7,455,238
Cash and cash equivalents	995,799				1,304,154					995,799	1,304,154	1,185,739
Accrued investment income	55,666				70,305					55,666	70,305
Other assets	59,897				74,964					59,897	74,964
Total assets	7,216,230				9,333,642					7,216,230	9,333,642
Liabilities:
Senior notes	170,515				376,329					170,515	376,329
Convertible senior notes	345,000				345,000					345,000	345,000
Convertible junior debentures (note 8)	344,422				315,626					344,422	315,626
Other liabilities	312,283				349,337					312,283	349,337
Total liabilities	6,019,415				7,664,587					6,019,415	7,664,587
Shareholders' equity
Common stock, one dollar par value, shares authorized 460,000; shares issued 2011 and 2010 - 205,047; outstanding 2011 - 201,172; 2010 - 200,450	205,047				205,047					205,047	205,047
Paid-in capital	1,135,821				1,138,942					1,135,821	1,138,942
Treasury stock (shares at cost 2011 - 3,875; 2010 - 4,597)	(162,542)				(222,632)					(162,542)	(222,632)
Accumulated other comprehensive income, net of tax	30,124				22,136					30,124	22,136
Retained earnings	(11,635)				525,562					(11,635)	525,562
Total shareholders' equity	1,196,815				1,669,055					1,196,815	1,669,055
Total liabilities and shareholders' equity	7,216,230				9,333,642					7,216,230	9,333,642
Parenthetical information [Abstract]
Fixed maturities, amortized cost	5,700,894				7,366,808					5,700,894	7,366,808
Common stock, par value (in dollars per share)	$ 1				$ 1					$ 1	$ 1
Common stock, shares authorized (in shares)	460,000				460,000					460,000	460,000
Common stock, shares issued (in shares)	205,047				205,047					205,047	205,047
Common stock, shares outstanding (in shares)	201,172				200,450					201,172	200,450
Treasury stock, shares at cost (in shares)	3,875				4,597					3,875	4,597
Revenues:
Investment income, net of expenses	40,339	48,898	55,490	56,543	57,061		58,465	62,868	68,859	201,270	247,253	304,678
Realized investment gains (losses), net										143,430	102,581	92,874
Other income										36,459	11,588	49,573
Total revenues										1,504,279	1,520,525	1,708,526
Expenses:
Interest expense	25,142	25,761	26,326	26,042	25,770	[1]	26,702	25,099	21,018	103,271	98,589	89,266
Total losses and expenses										1,988,578	1,879,925	3,473,579
Loss before tax and joint ventures										(484,299)	(359,400)	(1,765,053)
(Credit) provision for income tax										1,593	4,335	(442,776)
Net loss	(135,294)	(165,205)	(151,732)	(33,661)	(186,667)	[1]	(51,528)	24,551	(150,091)	(485,892)	(363,735)	(1,322,277)
Comprehensive loss										(477,904)	(415,754)	(1,141,333)
Cash flows from operating activities:
Net loss	(135,294)	(165,205)	(151,732)	(33,661)	(186,667)	[1]	(51,528)	24,551	(150,091)	(485,892)	(363,735)	(1,322,277)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Other										14,218	13,646	(55,764)
(Increase) decrease in accrued investment income										(14,639)	(9,523)	(11,028)
Net cash (used in) provided by operating activities										(1,883,851)	(875,430)	329,954
Cash flows from investing activities:
Purchase of fixed maturities										(4,393,471)	(5,225,794)	(4,147,412)
Sale of fixed maturities										4,742,213	4,287,312	3,663,239
Net cash used in investing activities										1,754,217	(111,904)	52,803
Cash flows from financing activities:
Repayment of note payable										0	0	(200,000)
Repayment of long-term debt										(178,721)	(1,000)	(94,352)
Common stock shares issued										0	772,376	0
Net cash (used in) provided by financing activities										(178,721)	1,105,749	(294,352)
Net (decrease) increase in cash and cash equivalents										(308,355)	118,415	88,405
Cash and cash equivalents at beginning of year				1,304,154					1,185,739	1,304,154	1,185,739	1,097,334
Cash and cash equivalents at end of year	995,799				1,304,154					995,799	1,304,154	1,185,739
Dividends and Dividend Restrictions [Abstract]
Percentage of statutory policyholders' surplus used to determine maximum allowable dividends (in hundredths)	10.00%									10.00%
Parent Company [Member]
Assets
Fixed maturities (amortized cost, 2011-$421,250; 2010-$844,383)	428,985				832,484					428,985	832,484
Cash and cash equivalents	57,636				58,380					57,636	58,380	79,160
Investment in subsidiaries, at equity in net assets	1,544,017				1,786,522					1,544,017	1,786,522
Accounts receivable - affiliates	0				686					0	686
Income taxes receivable	23,864				21,412					23,864	21,412
Accrued investment income	3,720				5,610					3,720	5,610
Other assets	11,785				16,530					11,785	16,530
Total assets	2,070,007				2,721,624					2,070,007	2,721,624
Liabilities:
Senior notes	170,515				376,329					170,515	376,329
Convertible senior notes	345,000				345,000					345,000	345,000
Convertible junior debentures (note 8)	344,422				315,626					344,422	315,626
Accounts payable - affiliates	84				0					84	0
Accrued interest	13,171				15,609					13,171	15,609
Other liabilities	0				5					0	5
Total liabilities	873,192				1,052,569					873,192	1,052,569
Shareholders' equity
Common stock, one dollar par value, shares authorized 460,000; shares issued 2011 and 2010 - 205,047; outstanding 2011 - 201,172; 2010 - 200,450	205,047				205,047					205,047	205,047
Paid-in capital	1,135,821				1,138,942					1,135,821	1,138,942
Treasury stock (shares at cost 2011 - 3,875; 2010 - 4,597)	(162,542)				(222,632)					(162,542)	(222,632)
Accumulated other comprehensive income, net of tax	30,124				22,136					30,124	22,136
Retained earnings	(11,635)				525,562					(11,635)	525,562
Total shareholders' equity	1,196,815				1,669,055					1,196,815	1,669,055
Total liabilities and shareholders' equity	2,070,007				2,721,624					2,070,007	2,721,624
Parenthetical information [Abstract]
Fixed maturities, amortized cost	421,250				844,383					421,250	844,383
Common stock, par value (in dollars per share)	$ 1				$ 1					$ 1	$ 1
Common stock, shares authorized (in shares)	460,000				460,000					460,000	460,000
Common stock, shares issued (in shares)	205,047				205,047					205,047	205,047
Common stock, shares outstanding (in shares)	201,172				200,450					201,172	200,450
Treasury stock, shares at cost (in shares)	3,875				4,597					3,875	4,597
Revenues:
Equity in undistributed net loss of subsidiaries										(437,731)	(270,844)	(1,326,671)
Investment income, net of expenses										15,693	5,573	1,026
Realized investment gains (losses), net										4,724	163	(38)
Other income										27,688	0	27,378
Total revenues										(389,626)	(265,108)	(1,298,305)
Expenses:
Operating expenses										(133)	2,116	350
Interest expense										103,271	98,589	89,266
Total losses and expenses										103,138	100,705	89,616
Loss before tax and joint ventures										(492,764)	(365,813)	(1,387,921)
(Credit) provision for income tax										(6,872)	(2,078)	(65,644)
Net loss										(485,892)	(363,735)	(1,322,277)
Other comprehensive (loss) income, net										7,988	(52,019)	180,944
Comprehensive loss										(477,904)	(415,754)	(1,141,333)
Cash flows from operating activities:
Net loss										(485,892)	(363,735)	(1,322,277)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Equity in undistributed net loss of subsidiaries										437,731	270,844	1,326,671
Other										7,378	40,638	1,842
Decrease (increase) in accounts receivable - affiliates										770	658	(41)
Decrease (increase) in income taxes receivable										(2,452)	6,330	(54,755)
(Increase) decrease in accrued investment income										1,890	(5,474)	267
(Decrease) increase in accrued interest										(2,438)	(33,795)	33,286
Net cash (used in) provided by operating activities										(43,013)	(84,534)	(15,007)
Cash flows from investing activities:
Transactions with subsidiaries										(200,000)	(200,000)	(1,050)
Purchase of fixed maturities										(130,503)	(977,408)	(6,618)
Sale of fixed maturities										551,493	135,413	2,336
Net cash used in investing activities										220,990	(1,041,995)	(5,332)
Cash flows from financing activities:
Repayment of note payable										0	0	(200,000)
Repayment of long-term debt										(178,721)	(1,000)	(94,352)
Net proceeds from convertible senior notes										0	334,373	0
Common stock shares issued										0	772,376	0
Net cash (used in) provided by financing activities										(178,721)	1,105,749	(294,352)
Net (decrease) increase in cash and cash equivalents										(744)	(20,780)	(314,691)
Cash and cash equivalents at beginning of year				58,380					79,160	58,380	79,160	393,851
Cash and cash equivalents at end of year	$ 57,636				$ 58,380					$ 57,636	$ 58,380	$ 79,160
Dividends and Dividend Restrictions [Abstract]
Percentage of statutory policyholders' surplus used to determine maximum allowable dividends (in hundredths)	10.00%									10.00%

[1] In prior periods, the liability associated with premium to be returned on claim payments is included in loss reserves and changes to this estimate affect losses incurred. See Note 3 - Summary of significant accounting policies - Revenue recognition.