Stockholders' Equity - Share repurchase programs (Details) - USD ($) $ in Thousands, shares in Millions	9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Oct. 31, 2017	Jan. 31, 2017	Aug. 31, 2015
Stockholders' Equity
Number of shares of common stock issued	0.7
Program Amount authorized to repurchase			$ 100,000	$ 100,000	$ 100,000
Repurchase of common stock (in shares)	0.0	0.9
Repurchase of common stock		$ 40,500