Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Available-for-sale securities

Details of available-for-sale securities were as follows:

December 31, 2017	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	10,342	$	4	$	129	$	10,217
U.S. Treasury securities	205		—		1		204
Total	$	10,547	$	4	$	130	$	10,421

December 31, 2016	Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(In thousands)
Mortgage-backed securities	$	10,546	$	8	$	105	$	10,449
Total	$	10,546	$	8	$	105	$	10,449

Assets and liabilities measured at fair value on a recurring basis

The Company's assets measured at fair value on a recurring basis were as follows:

	Fair Value Measurements at December 31, 2017, Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Balance at December 31, 2017
	(In thousands)
Assets:
Money market funds	$	—	$	6,965	$	—	$	6,965
Insurance contract*	—		77,388		—		77,388
Available-for-sale securities:
Mortgage-backed securities	—		10,217		—		10,217
U.S. Treasury securities	—		204		—		204
Total assets measured at fair value	$	—	$	94,774	$	—	$	94,774

* The insurance contract invests approximately 49 percent in fixed-income investments, 23 percent in common stock of large-cap companies, 14 percent in common stock of mid-cap companies, 11 percent in common stock of small-cap companies, 2 percent in target date investments and 1 percent in cash equivalents.

	Fair Value Measurements at December 31, 2016, Using
	Quoted Prices in Active Markets for Identical Assets  (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Balance at December 31, 2016
	(In thousands)
Assets:
Money market funds	$	—	$	1,602	$	—	$	1,602
Insurance contract*	—		70,921		—		70,921
Available-for-sale securities:
Mortgage-backed securities	—		10,449		—		10,449
Total assets measured at fair value	$	—	$	82,972	$	—	$	82,972

* The insurance contract invests approximately 52 percent in fixed-income investments, 22 percent in common stock of large-cap companies, 13 percent in common stock of mid-cap companies, 10 percent in common stock of small-cap companies, 1 percent in target date investments and 2 percent in cash equivalents.

Fair value of long-term debt outstanding

The estimated fair value of the Company's Level 2 long-term debt at December 31 was as follows:

	2017				2016
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
	(In thousands)
Long-term debt	$	1,714,853	$	1,826,256	$	1,790,159	$	1,841,885