Employee Stock Benefit Plans Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	6 Months Ended	12 Months Ended
	May 08, 2016	Nov. 27, 2017	Dec. 31, 2017
Summary of stock option activity - Shares
Granted (in shares)	341,450	490,000
Options to purchase common stock
Summary of stock option activity - Shares
Options outstanding at the beginning of the period (in shares)			6,374,000
Granted (in shares)			2,094,000
Exercised (in shares)			(1,385,000)
Canceled (in shares)			(1,340,000)
Expired (in shares)			(95,000)
Options outstanding at the end of the period (in shares)			5,648,000
Options exercisable at the end of the period (in shares)			2,934,000
Summary of stock option activity - Weighted-Average Exercise Price (in dollars per share)
Options outstanding at the beginning of the period (in dollars per share)			$ 31.60
Granted (in dollars per share)			42.82
Exercised (in dollars per share)			12.62
Canceled (in dollars per share)			41.22
Expired (in dollars per share)			57.56
Options outstanding at the end of the period (in dollars per share)			37.71
Options exercisable at the end of the period (in dollars per share)			$ 33.23
Weighted-Average Contractual Life (In Years)
Options outstanding at the end of the period			7 years 11 days
Options exercisable at the end of the period			5 years 161 days
Aggregate Intrinsic Value
Options outstanding at the end of the period			$ 23,150
Options exercisable at the end of the period			$ 21,365