7. Debt and lines of credit

Short-term borrowings

We maintain a line of credit to support commercial paper borrowings, if any, and to provide additional liquidity through bank loans. As of June 30, 2018, we had a variable-rate revolving credit facility from a consortium of investment-grade banks that allows us to borrow up to $2 billion until March 2023. The interest rate on borrowings under this credit facility, if drawn, is indexed to the applicable London Interbank Offered Rate (LIBOR). As of June 30, 2018, our credit facility was undrawn, and we had no commercial paper outstanding.

Long-term debt

We retired $500 million of maturing debt in May 2018.

In the second quarter of 2018, we issued an aggregate principal amount of $1.5 billion of fixed-rate, long-term debt due in 2048, comprised of the issuance of $1.3 billion in May 2018 and an additional $200 million in June 2018. We incurred $16 million of issuance and other related costs. We received $1.5 billion in proceeds, net of the original issuance discount and premium, to be used for general corporate purposes.

Long-term debt outstanding is as follows:

	June 30,			December 31,
	2018			2017
Notes due 2018 at 1.00%	$	—		$	500
Notes due 2019 at 1.65%		750			750
Notes due 2020 at 1.75%		500			500
Notes due 2021 at 2.75%		550			550
Notes due 2022 at 1.85%		500			500
Notes due 2023 at 2.25%		500			500
Notes due 2024 at 2.625%		300			300
Notes due 2027 at 2.90%		500			500
Notes due 2048 at 4.15%		1,500			—
Total debt		5,100			4,100
Net unamortized discounts, premiums and debt issuance costs		(34	)		(23	)
Total debt, including net unamortized discounts, premiums and debt issuance costs		5,066			4,077
Current portion of long-term debt		—			(500	)
Long-term debt	$	5,066		$	3,577

Interest and debt expense was $30 million and $20 million for the second quarters of 2018 and 2017, respectively, and $53 million and $38 million for the first six months of 2018 and 2017, respectively. This was net of the amortization of the debt discounts, premiums and debt issuance costs. Capitalized interest was not material.