Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Net income	$ 19,182		$ 5,080		$ 34,669		$ 10,131
Amortization of prior service credit included in net periodic cost, net of tax of $(871), $(899), $(1,741) and $(1,712)	1,361	[1]	1,405	[1]	2,723	[1]	2,678	[1]
Amortization of actuarial loss included in net periodic cost, net of tax of $2,267, $1,777, $4,513 and $3,604	3,544	[1]	2,780	[1]	7,057	[1]	5,638	[1]
Other comprehensive income, net of tax	2,183	[1]	1,375	[1]	4,334	[1]	2,960	[1]
Comprehensive income	$ 21,365		$ 6,455		$ 39,003		$ 13,091

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