Consolidated Statements Of Changes In Equity (USD $) In Thousands	Common Shares $1 Par Value [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Subtotal [Member]	Noncontrolling Interest [Member]	Total
Balance, at Dec. 31, 2010	$ 243,808	$ 1,542,964	$ 1,687,363	$ 3,482,623	$ 6,956,758	$ 6,623	$ 6,963,381
Net income				10,507	10,507	279	10,786
Other comprehensive loss, net of taxes			(65,058)		(65,058)		(65,058)
Contributions from noncontrolling interests						190	190
Distributions to noncontrolling interests						(3,567)	(3,567)
Change in interest in consolidated subsidiary		(1,912)			(1,912)	1,912
Share-based compensation expense		1,024			1,024		1,024
Exercise of warrants to purchase common shares	523	(523)
Exercise of options to purchase common shares, including excess tax benefit	48	1,307			1,355		1,355
Balance, at Mar. 31, 2011	244,379	1,542,860	1,622,305	3,493,130	6,902,674	5,437	6,908,111
Balance, at Dec. 31, 2011	244,583	1,570,684	912,421	3,446,708	6,174,396	3,865	6,178,261
Net income				490,877	490,877	202	491,079
Other comprehensive loss, net of taxes			(240,842)		(240,842)		(240,842)
Contributions from noncontrolling interests						26	26
Distributions to noncontrolling interests						(1,576)	(1,576)
Change in fair value of redeemable noncontrolling interests		(644)			(644)		(644)
Share-based compensation expense		3,892			3,892		3,892
Balance, at Mar. 31, 2012	$ 244,583	$ 1,573,932	$ 671,579	$ 3,937,585	$ 6,427,679	$ 2,517	$ 6,430,196