CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 308,536	[1]	$ 323,756	[1]	$ 223,311	[1]
Other comprehensive income (loss):
Change in net unrealized gains (losses) on investments, net of income tax: (2012 - $392,372; 2011 - $400,626; 2010 - $328,597)	728,692		744,032	[1]	609,694	[1]
Reclassification adjustment for investment amounts included in net income, net of income tax: (2012 - $(3,317); 2011 - $(14,646); 2010 - $(5,951))	(6,163)		(27,213)	[1]	(10,989)	[1]
Change in net unrealized gains (losses) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings, net of income tax: (2012 - $16,227; 2011 - $(13,195); 2010 - $11,515)	30,136		(24,506)	[1]	21,384	[1]
Change in accumulated (loss) gain - derivatives, net of income tax: (2012 - $2,609; 2011 - $2,382; 2010 - $4,441)	4,846		4,424	[1]	7,630	[1]
Reclassification adjustment for derivative amounts included in net income, net of income tax: (2012 - $(381); 2011 - $(138); 2010 - $(614))	(708)		(256)	[1]	(1,105)	[1]
Total other comprehensive income	756,803	[1]	696,481	[1]	626,614	[1]
Total comprehensive income	$ 1,065,339	[1]	$ 1,020,237	[1]	$ 849,925	[1]

[1] Recast from previously reported information