Income Taxes (Details) (USD $) In Thousands, 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
Differences between our effective tax rate for financial statement purposes and the Federal statutory rate
Statutory tax rate									35.00%	35.00%	35.00%
Federal tax at statutory rate									$ 124,252	$ 171,439	$ 181,493
Nontaxable municipal bond interest and dividend received deduction									(29,021)	(26,968)	(24,109)
State income taxes, net of federal tax benefit									3,050	2,397	4,107
Foreign income taxes									25,410	32,008	32,319
Foreign tax credits									(25,410)	(32,008)	(32,310)
Uncertain tax positions (net of federal tax benefit (expense) on state positions: $212 in 2011, $(52) in 2010 and $(88) in 2009)									38	(1,532)	(1,704)
Other, net									1,444	(605)	4,887
Income tax expense	$ 34,092	$ 22,355	$ 27,427	$ 15,889	$ 37,738	$ 38,949	$ 36,373	$ 31,671	$ 99,763	$ 144,731	$ 164,683
Effective tax rate									28.10%	29.50%	31.80%