Selected Quarterly Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Data [Abstract]

Schedule of selected quarterly data (unaudited)

	2015 Quarter Ended										2014 Quarter Ended
In thousands, except per share amounts	December 31		September 30			June 30			March 31		December 31		September 30		June 30		March 31
Revenues	$	129,815	$	121,968		$	122,345		$	121,173	$	146,518	$	134,121	$	140,310	$	132,727
Operating income (loss)	6,792		(205,438		)	8,057			3,015		14,656		10,540		10,987		4,579
Net income (loss)	2,543		(170,914		)	(4,172		)	1,615		10,089		6,420		5,637		1,845
Basic earnings (loss) per share	$	0.04	$	(2.77	)	$	(0.07	)	$	0.03	$	0.16	$	0.10	$	0.09	$	0.03
Diluted earnings (loss) per share	$	0.04	$	(2.77	)	$	(0.07	)	$	0.03	$	0.16	$	0.10	$	0.09	$	0.03