Income taxes (Tables)

3 Months Ended

Mar. 31, 2013

Income Tax Disclosure [Abstract]

Schedule of Income Taxes

Income taxes:

	Three months ended
	March 31,
	2012			2013
	(In thousands)
Expected income tax expense, at statutory rate	$	4,092		$	3,811
U.S. state income tax expense, net		507			497
Other, net		(175	)		(83	)
Income tax expense	$	4,424		$	4,225
Comprehensive provision for income taxes allocable to:
Net income	$	4,424		$	4,225
Other comprehensive income (loss):
Pension plans		1,882			1,760
OPEB plans		(841	)		(865	)
	$	5,465		$	5,120