Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Net income	$ 16,270		$ 19,182		$ 36,620		$ 34,669
Other comprehensive income, net of tax:
Amortization of prior service credit included in net periodic cost, net of tax of $(867) and $(871), $(1,734) and $(1,741)	(1,356)	[1]	(1,361)	[1]	(2,712)	[1]	(2,723)	[1]
Amortization of actuarial loss included in net periodic cost, net of tax of $1,568 and $2,267, $3,245 and $4,513	2,452	[1]	3,544	[1]	5,074	[1]	7,057	[1]
Other comprehensive income, net of tax	1,096	[1]	2,183	[1]	2,362	[1]	4,334	[1]
Comprehensive income	$ 17,366		$ 21,365		$ 38,982	[1]	$ 39,003

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