CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - Parenthetical - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Stockholders' Equity [Abstract]
Actuarially Determined Long-Term Liability Adjustments, Tax	$ 1,183	$ 1,819	$ 2,464	$ 3,786
Retirement of common stock (in shares)			91,000