Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

The estimated fair values of our financial instruments as of March 31, 2013 and December 31, 2012 have been calculated based upon available market information, and are presented below by level in the fair value hierarchy:

	March 31, 2013				December 31, 2012
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Level 1:
Subordinated convertible debentures	$	17	$	22	$	55	$	63
Senior and senior subordinated notes	5,386		5,921		5,387		5,881
Level 2:
4 percent Convertible Senior Notes (1)	139		155		137		155

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(1) The fair value of the 4 percent Convertible Senior Notes is based on the market value of comparable notes. Consistent with the carrying amount, the fair value excludes the equity component of the notes. To exclude the equity component and calculate the fair value, we used an effective interest rate of 6.7 percent.