Long-Term Debt (Tables)

6 Months Ended

Jun. 30, 2017

Debt Disclosure [Abstract]

Long-Term Debt

	June 30,			December 31,			June 30,
	2017			2016			2016
	(Dollars in Thousands)
6.6% Senior Notes, due 2018	$	299,676		$	299,483		$	299,294
7% Debentures, due 2025		124,134			124,090			124,046
6.25% Senior Notes, due 2037		228,003			227,975			227,947
4.25% Senior Notes, due 2024		395,532			395,252			394,977
3.45% Senior Notes, due 2027		296,456			—			—
Floating Rate Notes, due 2020, interest rate of 1.82% at    June 30, 2017		297,847			—			—
Floating Rate Notes, due 2017, interest rate of 2.10% and 1.73% at    December 31, 2016 and June 30, 2016, respectively		—			299,033			298,793
Term Loan Facility, due 2018, interest rate of 1.96% at June 30, 2016		—			—			213,571
Revolving Facility, due 2021, interest rate of 1.86%    at December 31, 2016		—			160,000			—
Trade Receivable Facility, interest rate of 1.78%, 1.34% and 1.16% at    June 30, 2017, December 31, 2016 and June 30, 2016,    respectively		140,000			180,000			220,000
Other notes		333			356			589
Total debt		1,781,981			1,686,189			1,779,217
Less: Current maturities of long-term debt and short-term facilities		(140,037	)		(180,036	)		(238,155	)
Long-term debt	$	1,641,944		$	1,506,153		$	1,541,062