Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Consolidated Debt

Debt

Long-term debt at December 31, 2016 and 2017 was as follows (in thousands):

	December 31,
	2016			2017
Commercial paper	$	50,000		$	—
6.40% Notes due 2018	250,000			250,000
6.55% Notes due 2019	550,000			550,000
4.25% Notes due 2021	550,000			550,000
3.20% Notes due 2025	250,000			250,000
5.00% Notes due 2026	650,000			650,000
6.40% Notes due 2037	250,000			250,000
4.20% Notes due 2042	250,000			250,000
5.15% Notes due 2043	550,000			550,000
4.20% Notes due 2045	250,000			250,000
4.25% Notes due 2046	500,000			500,000
4.20% Notes due 2047	—			500,000
Face value of long-term debt	4,100,000			4,550,000
Unamortized debt issuance costs(1)	(26,948		)	(29,472		)
Net unamortized debt premium(1)	6,530			215
Net unamortized amount of gains from historical fair value hedges(1)	7,610			3,749
Long-term debt, net, including current portion	4,087,192			4,524,492
Less: current portion of long-term debt, net	—			250,974
Long-term debt, net	$	4,087,192		$	4,273,518

(1) Debt issuance costs, note discounts and premiums, and realized gains and losses of historical fair value hedges are being amortized or accreted to the applicable notes over the respective lives of those notes.