Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Redeemable noncontrolling interest redemption value	$ 60,665	$ 64,935
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	89,717,000	80,609,000
Treasury stock, shares	32,680,000	32,028,000