Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 19,228	$ 20,230	$ 24,178	$ 27,847
Defined benefit pension plans
Actuarial gain, net of tax of $-, $7,422, $-, and $7,422, respectively	0	11,923	0	11,923
Amortization of actuarial loss, net of tax of $184, $504, $368, and $1,117, respectively	294	808	588	1,793
Effect of settlements, net of tax of $-, $-, $114, and $192, respectively	0	0	183	309
Other comprehensive income, net of tax	294	12,731	771	14,025
Comprehensive income	$ 19,522	$ 32,961	$ 24,949	$ 41,872