Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 3,475	$ 3,661
Accumulated depreciation	200,193	188,720
Accumulated amortization	$ 14,815	$ 12,655
Common stock, $0.01 par value	$ 0.01	$ 0.01
Common stock shares authorized	100,000	100,000
Common stock shares issued	42,673	42,533
Treasury stock shares	449	438