Consolidated Statements Of Operations And Comprehensive Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
REVENUES:
Gross premiums written	$ 1,939,521	$ 1,758,397	$ 1,696,345
Premiums ceded	(405,755)	(365,942)	(375,220)
Net premiums written	1,533,766	1,392,455	1,321,125
Change in unearned premiums	(76,774)	(32,907)	(4,233)
Net premiums earned	1,456,992	1,359,548	1,316,892
Net investment income	195,948	244,143	300,675
Net realized investment gains (losses)	10,077	285,612	126,352
Net impairment charges recognized in earnings:
Total other-than-temporary impairment charges		(168)	(68,236)
Portion of loss recognized in other comprehensive income, before taxes			18,659
Net impairment charges recognized in earnings		(168)	(49,577)
Other income	101,744	913	1,506
Total revenues	1,764,761	1,890,048	1,695,848
EXPENSES:
Net losses and loss expenses	959,156	707,883	604,060
Acquisition costs	167,295	159,489	148,847
General and administrative expenses	271,656	286,557	248,592
Amortization and impairment of intangible assets	2,978	3,483	11,051
Interest expense	54,989	40,242	39,019
Foreign exchange loss	3,159	444	748
Total expenses	1,459,233	1,198,098	1,052,317
Income before income taxes	305,528	691,950	643,531
Income tax expense	30,980	26,945	36,644
NET INCOME	274,548	665,005	606,887
Other comprehensive (loss) income:
Unrealized gains on investments arising during the year net of applicable deferred income tax expense	5,243	162,653	243,188
Portion of other-than-temporary impairment losses recognized in other comprehensive income			(18,659)
Reclassification adjustment for net realized investment gains included in net income, net of applicable income tax	(47,894)	(213,478)	(43,464)
Other comprehensive (loss) income	(42,651)	(50,825)	181,065
COMPREHENSIVE INCOME	$ 231,897	$ 614,180	$ 787,952
PER SHARE DATA
Basic earnings per share	$ 7.21	$ 14.30	$ 12.26
Diluted earnings per share	$ 6.92	$ 13.32	$ 11.67
Weighted average common shares outstanding	38,093,351	46,491,279	49,503,438
Weighted average common shares and common share equivalents outstanding	39,667,905	49,913,317	51,992,674
Dividends paid per share	$ 0.75	$ 1.05	$ 0.74