Quarterly Financial Data (Summary of Quarterly Financial Data) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Data [Abstract]
Revenue	$ 71,234	$ 65,767	$ 68,564	$ 75,885	$ 64,853	$ 82,013	$ 95,253	$ 98,001	$ 281,450		$ 340,120		$ 241,171
Operating income	8,237	7,946	10,987	13,745	3,549	10,986	12,631	16,459
Net income (loss)	$ (3,827)	$ 4,322	$ 5,853	$ 6,162	$ 544	$ 5,144	$ 6,853	$ 7,591	$ 12,510	[1]	$ 20,132	[1]	10,219	[1]
Basic income per common share	$ (0.13)	$ 0.14	$ 0.19	$ 0.21	$ 0.02	$ 0.17	$ 0.23	$ 0.25
Acquisition deal costs													$ 8,057

[1] *There is no material difference between net income and comprehensive income.