Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Receivables, allowance	$ 13,157	$ 11,308
Intangible assets, accumulated amortization	$ 61,358	$ 54,184
Preferred stock, shares authorized	500,000	500,000
Preferred stock, shares issued	0	0
Common stock, par value (in usd per share)	$ 0.30	$ 0.30
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	29,987,232	29,953,041