Debt (Tables)

3 Months Ended

Mar. 31, 2018

Debt Disclosure [Abstract]

Schedule of Long-Term Debt

	March 31, 2018			December 31, 2017
5.72% Notes, due 2019	—			500
1.63% Convertible Notes, due 2019	403			403
6.150% Notes, due 2020	1,000			1,000
5.40% Notes due 2021	1,250			1,250
5.87% Notes, due 2022	627			627
5.125% Notes, due 2024	1,250			1,250
5.90% Notes, due 2027	625			625
6.75% Bonds, due 2028	300			300
5.95% Notes, due 2037	625			625
Iowa Finance Authority Loan, due 2042	250			250
Other(1)	(18		)	(23		)
Total debt	6,312			6,807
Less: amount due within one year	3			1
Total long-term debt	$	6,309		$	6,806

⁽¹⁾  Includes various financing arrangements related to subsidiaries, unamortized debt discounts related to outstanding notes and bonds listed in the table above, an equity option related to the convertible notes due in 2019, and unamortized debt issuance costs.