Condensed Consolidated Statements of Stockholders' Equity - 6 months ended Jun. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2016	$ 1,273,290	$ 811	$ (3,869)	$ 1,129,051	$ 163,173	$ (15,876)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	31,981				31,981
Unrealized loss on derivatives	(39)					(39)
Pension and post-retirement liability	(1,402)					(1,402)
Cash dividend declared ($0.125 per share)	(10,195)				(10,195)
Equity-based compensation	11,952			11,952
Proceeds from options exercised	547		815	(268)
Issuance of restricted stock	0		1,724	(1,724)
Shares withheld for employee taxes related to vested restricted stock and stock units	(3,926)	1	839	(4,766)
Ending Balance at Jun. 30, 2017	$ 1,302,208	$ 812	$ (491)	$ 1,134,245	$ 184,959	$ (17,317)