Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 22,154	$ 19,228	$ 32,174	$ 24,178
Defined benefit pension plans
Amortization of actuarial loss, net of tax of $158, $184, $310 and $368, respectively	252	294	495	588
Effect of settlements, net of tax of $-, $-, $- and $114, respectively	0	0	0	183
Other comprehensive income, net of tax	252	294	495	771
Comprehensive income	$ 22,406	$ 19,522	$ 32,669	$ 24,949