Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Consolidated Balance Sheets [Abstract]
Allowance for trade accounts receivable	$ 2,670	$ 2,032
Unamortized premium on notes	$ 956	$ 1,217
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	80,000,000	80,000,000
Common stock, shares issued	43,500,032	43,500,032
Common stock, shares outstanding	42,196,680	42,241,719
Treasury stock, shares	1,303,352	1,258,313