CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Reclassification of net unrealized loss on interest rate swaps during the period, net of tax	$ 50	$ 460
Net unrealized gain (loss) from pension and postretirement plans, tax	113	(186)
Reclassification of net unrealized loss on energy derivative instruments during the period, net of tax	(187)	57
Subsidiaries [Member]
Reclassification of net unrealized loss on interest rate swaps during the period, net of tax	1,078	1,823
Net unrealized gain (loss) from pension and postretirement plans, tax	(386)	(975)
Reclassification of net unrealized loss on energy derivative instruments during the period, net of tax	$ (43)	$ (43)