Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Consolidated net income	$ 6,274	$ 7,954	$ 26,039	$ 20,305
Other comprehensive income (loss), net of tax
Amortization of unrealized pension and postretirement gain (loss), net of tax	(4)	10	(11)	314
Unrealized gain (loss) on investments, net of tax	263	(231)	1,174	(738)
Unrealized loss on interest rate swaps, net of tax	(208)	(233)	(1,616)	(308)
Other comprehensive income (loss), net of tax	51	(454)	(453)	(732)
Consolidated comprehensive income	$ 6,325	$ 7,500	$ 25,586	$ 19,573