Investments (Summary Of Investments Current And Non-Current) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Investments [Line Items]
Total current investments	$ 193,742	$ 150,135
Total non-current investments	1,542,199	2,226,875
Amortized Cost [Member]
Schedule of Investments [Line Items]
Investments available for sale - current	189,467	146,594
Other investments, including accrued interest income	4,188	4,113
Total current investments	193,655	150,707
Total non-current investments	1,413,340	1,517,649
Amortized Cost [Member] \| Fortescue [Member]
Schedule of Investments [Line Items]
Investments available for sale - non-current	27,100	115,703
Amortized Cost [Member] \| Inmet Mining Corporation [Member]
Schedule of Investments [Line Items]
Investments available for sale - non-current	504,006	504,006
Amortized Cost [Member] \| Private Equity Funds [Member]
Schedule of Investments [Line Items]
Other investments - non-current	81,481	85,528
Carrying Value And Estimated Fair Value [Member]
Schedule of Investments [Line Items]
Investments available for sale - current	189,474	145,977
Other investments, including accrued interest income	4,268	4,158
Total current investments	193,742	150,135
Total non-current investments	1,542,199	2,226,875
Carrying Value And Estimated Fair Value [Member] \| Fortescue [Member]
Schedule of Investments [Line Items]
Investments available for sale - non-current	153,438	569,256
Carrying Value And Estimated Fair Value [Member] \| Inmet Mining Corporation [Member]
Schedule of Investments [Line Items]
Investments available for sale - non-current	453,276	708,193
Carrying Value And Estimated Fair Value [Member] \| Private Equity Funds [Member]
Schedule of Investments [Line Items]
Other investments - non-current	81,481	85,528
Other Investments Available For Sale [Member] \| Amortized Cost [Member]
Schedule of Investments [Line Items]
Investments available for sale - non-current	711,655	724,664
Other Investments Available For Sale [Member] \| Carrying Value And Estimated Fair Value [Member]
Schedule of Investments [Line Items]
Investments available for sale - non-current	765,118	776,444
Other Non-Publicly Traded Investments [Member] \| Amortized Cost [Member]
Schedule of Investments [Line Items]
Other investments - non-current	45,861	46,947
Other Non-Publicly Traded Investments [Member] \| Carrying Value And Estimated Fair Value [Member]
Schedule of Investments [Line Items]
Other investments - non-current	45,649	46,653
FMG Zero Coupon Note Component [Member] \| Amortized Cost [Member]
Schedule of Investments [Line Items]
Other investments - non-current	43,237	40,801
FMG Zero Coupon Note Component [Member] \| Carrying Value And Estimated Fair Value [Member]
Schedule of Investments [Line Items]
Other investments - non-current	$ 43,237	$ 40,801

Investments in debt and equity securities which are categorized neither as trading securities nor held-to-maturity securities and which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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+ Details

- Definition

Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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+ Details