Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value of Financial Instruments
Carrying Value	$ 4,151,824	$ 4,448,888
Fair Value	4,557,032	5,142,918
Subsidiary preferred stock, carrying value	69,188	69,188
Subsidiary preferred stock, fair value	70,500	68,625
Securities available-for-sale	99,832	200,577
Trading equity securities, fair value		52,705
6.15% senior notes due February 2018
Fair Value of Financial Instruments
Carrying Value	969,318	968,708
Fair Value	1,082,328	1,164,813
Interest rate on senior note due (as a percent)	6.15%
9.25% senior notes due January 2019
Fair Value of Financial Instruments
Carrying Value	1,111,000	1,125,000
Fair Value	1,383,806	1,492,819
Interest rate on senior note due (as a percent)	9.25%
5.00% senior notes due September 2020
Fair Value of Financial Instruments
Carrying Value	697,795	697,648
Fair Value	717,535	770,707
Interest rate on senior note due (as a percent)	5.00%
4.625% senior notes due September 2021
Fair Value of Financial Instruments
Carrying Value	698,027	697,907
Fair Value	696,367	755,517
Interest rate on senior note due (as a percent)	4.625%
Revolving Credit Facility
Fair Value of Financial Instruments
Carrying Value	300,000	890,000
Fair Value	300,000	890,000
Other
Fair Value of Financial Instruments
Carrying Value	11,496	437
Fair Value	11,496	437
Commercial paper
Fair Value of Financial Instruments
Carrying Value	295,000
Fair Value	$ 295,000

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date before deducting unamortized discount or premiums (if any). May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Trading Securities which consist of all investments in certain debt and equity securities that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for which an entity has elected the fair value option. Trading generally reflects active and frequent buying and selling, and trading securities are generally used with the objective of generating profits on short-term differences in price, but this category of investments may also include items which are not intended to be sold in the near term or for which the fair value option has been elected.

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