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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair Value of Financial Instruments (Schedule of Estimated Fair Value of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	$ 115,109	$ 129,865	$ 191,432	$ 299,169
Cash and cash equivalents, fair value disclosure	115,109	129,865
Available-for-sale securities	33,943	31,582
Available-for-sale securities, fair value disclosure	33,943	31,582
Trading securities	34,946	30,486
Trading securities, fair value disclosure	34,946	30,486
Receivables Facility and Unsecured Debt [Member]
Liabilities:
Other debt	348,575	41,143
Other debt, fair value disclosure	348,575	41,143
Credit Facility, Type of Debt [Member] \| Credit Facility, Name [Member]
Liabilities:
Credit Facility	5,974,062	5,979,383
Credit Facility, fair value disclosure	5,870,228	5,780,877
Senior Notes [Member] \| Senior Notes at 8.875, Due 2015 [Member]
Liabilities:
Senior notes	931,235	1,777,617
Senior notes, fair value disclosure	961,193	1,842,322
Senior Notes [Member] \| Senior Notes at 8.0, Due 2019 [Member]
Liabilities:
Senior notes	2,023,955	1,000,000
Senior notes, fair value disclosure	$ 2,065,000	$ 995,000