Long-Term Debt (Tables)

9 Months Ended

Sep. 30, 2017

Debt Disclosure [Abstract]

Long-Term Debt

	September 30,			December 31,			September 30,
	2017			2016			2016
	(Dollars in Thousands)
6.60% Senior Notes, due 2018	$	299,774		$	299,483		$	299,388
7% Debentures, due 2025		124,157			124,090			124,068
6.25% Senior Notes, due 2037		228,018			227,975			227,961
4.25% Senior Notes, due 2024		395,673			395,252			395,115
3.450% Senior Notes, due 2027		296,551			—			—
Floating Rate Notes, due 2020, interest rate of 1.96% at    September 30, 2017		298,046			—			—
Floating Rate Notes, due 2017, interest rate of 2.10% and 1.94% at    December 31, 2016 and September 30, 2016, respectively		—			299,033			298,750
Term Loan Facility, due 2018, interest rate of 1.90% at    September 30, 2016		—			—			209,096
Revolving Facility, due 2021, interest rate of 1.86%    at December 31, 2016		—			160,000			—
Trade Receivable Facility, interest rate of 1.96%, 1.34% and 1.22% at    September 30, 2017, December 31, 2016 and September 30, 2016,    respectively		80,000			180,000			210,000
Other notes		321			356			457
Total debt		1,722,540			1,686,189			1,764,835
Less: Current maturities of long-term debt and short-term facilities		(80,038	)		(180,036	)		(228,025	)
Long-term debt	$	1,642,502		$	1,506,153		$	1,536,810