Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Investments, All Other Investments [Abstract]

Summary of Carrying Amounts and Estimated Fair Values of Other Financial Instruments

The following table summarizes the carrying amounts and estimated fair values of our other financial instruments at March 31, 2017:

	Carrying Amount		Fair Value
	(Dollars in thousands)
Assets:
Cash and cash equivalents	$	350,621	$	350,621
Natural gas swap agreements	402		402
Liabilities:
Bank debt	$	400,183	$	400,183
5% Senior Notes	500,000		506,875
5½% Senior Notes	300,000		308,250
4¾% Senior Notes	300,000		299,133
3¼% Senior Notes	692,380		691,051
Interest rate swap agreements	92		92