Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Allowance for trade accounts receivable	$ 3,304	$ 3,675
Unamortized premium on notes	$ 1,401	$ 1,459
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	43,170,095	42,226,088
Treasury stock, shares	329,937	1,273,944