Long-Term Debt (Tables)

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Long-Term Debt

	September 30,			December 31,			September 30,
	2018			2017			2017
	(Dollars in Thousands)
6.60% Senior Notes, due 2018	$	—		$	299,871		$	299,774
7% Debentures, due 2025		124,249			124,180			124,157
6.25% Senior Notes, due 2037		228,079			228,033			228,018
4.25% Senior Notes, due 2024		396,251			395,814			395,673
4.250% Senior Notes, due 2047		591,499			591,688			—
3.500% Senior Notes, due 2027		494,643			494,352			—
3.450% Senior Notes, due 2027		296,861			296,628			296,551
Floating Rate Senior Notes, due 2019, interest rate of 2.84%    and 2.13% at September 30, 2018 and December 31, 2017,    respectively		299,074			298,102			—
Floating Rate Notes, due 2020, interest rate of 2.96%, 2.10% and    1.96% at September 30, 2018, December 31, 2017 and September    30, 2017, respectively		298,773			298,227			298,046
Revolving Facility, due 2022, interest rate of 3.29% at    September 30, 2018		100,000			—			—
Trade Receivable Facility, interest rate of 2.83% and 1.96% at    September 30, 2018 and 2017, respectively		380,000			—			80,000
Other notes		269			308			321
Total debt		3,209,698			3,027,203			1,722,540
Less: Current maturities of long-term debt and short-term    facilities		(380,041	)		(299,909	)		(80,038	)
Long-term debt	$	2,829,657		$	2,727,294		$	1,642,502