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Common Stock (Details) (USD $) Share data in Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2012
Company's subsidiaries net assets restricted from being used to transfer funds to the Company | $ 2,000,000,000
Credit agreement limitation on company ratio of funded debt to capitalization (excluding subsidiaries) | 65.00%
Company's (excluding its subsidiaries) net assets restricted from use for dividend payments | $ 177,000,000
Parent company [Member] |
Shares of common stock reserved for original issuance under the Stock Purchase Plan and K-Plan (in shares) | 23.2
Centennial [Member] |
Maximum distributions to the company as a percentage of consolidated net income after taxes, excluding noncash write-downs, for the preceding fiscal year (in hundredths) | 100.00%

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