Cash flow information (Details 1) - USD ($)		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016
Interest, net of amount capitalized and AFUDC - borrowed of $676 and $842 in 2017 and 2016, respectively		$ 58,119,000	$ 66,281,000
Income taxes paid (refunded), net	[1]	46,430,000	73,771,000
Property, plant and equipment additions in accounts payable		16,914,000	22,560,000
Capitalized interest and AFUDC borrowed		676,000	842,000
Continuing and discontinued operations [Member]
Income taxes paid (refunded), net		$ 1,400,000	$ (144,000)

[1] Income taxes paid (refunded), net of discontinued operations, were $1.4 million and $(144,000) for the nine months ended September 30, 2017 and 2016, respectively.