Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, shares par value	$ 0.06	$ 0.06
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	89,037,000	90,436,000
Common stock, shares outstanding	89,037,000	90,436,000
Treasury stock, shares	3,093,000	2,971,000