Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Redeemable noncontrolling interest redemption value	$ 31,172	$ 60,665
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	90,003,000	89,717,000
Treasury stock, shares	32,803,000	32,680,000