Income Taxes (Schedule Of Effective Income Tax Rates) (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
Income Taxes [Abstract]
Income before income taxes	$ 195,052	$ (5,300)	$ 104,873	$ 10,903	$ 92,579	$ 268,089	$ 194,337	$ 136,945	$ 305,528	$ 691,950	$ 643,531
Expected tax rate									7.80%	7.80%	0.00%
Income not subject to income tax									(3.40%)	(7.80%)	0.00%
Foreign taxes at local expected tax rates									6.00%	3.70%	5.60%
Loss on sale of subsidiary									0.00%	(0.30%)	0.00%
Disallowed expenses and capital allowances									0.10%	0.10%	0.10%
Prior year refunds and adjustments									(0.60%)	0.60%	(0.10%)
Other									0.20%	(0.20%)	0.10%
Effective tax rate									10.10%	3.90%	5.70%