Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Net income	$ 22,191		$ 18,599		$ 56,860		$ 28,730
Amortization of prior service credit included in net periodic cost, net of tax of $(870), $(836), $(2,611) and $(2,548)	(1,362)	[1]	(1,308)	[1]	(4,085)	[1]	(3,986)	[1]
Amortization of actuarial loss included in net periodic cost, net of tax of $2,255, $1,801, $6,768 and $5,405	3,529	[1]	2,819	[1]	10,586	[1]	8,457	[1]
Other comprehensive income, net of tax	2,167	[1]	1,511	[1]	6,501	[1]	4,471	[1]
Comprehensive income	$ 24,358		$ 20,110		$ 63,361		$ 33,201

[1] (a) Amortization of prior service cost (credit) and amortization of actuarial loss are included in the computation of net periodic cost.