Condensed Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Customer receivables, allowances	$ 8,925	$ 8,976
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	140,000,000	140,000,000
Common stock, shares outstanding	83,649,398	84,411,878