Stockholders' Equity Repurchases of Common Stock (Details) - USD ($) shares in Thousands, $ in Thousands	1 Months Ended	9 Months Ended
	Oct. 31, 2018	Sep. 30, 2018	Oct. 01, 2017	Nov. 01, 2018	Aug. 15, 2018	Feb. 15, 2018	Feb. 22, 2017
Subsequent Event
Equity, Class of Treasury Stock
Treasury Stock, Shares, Acquired	1,596
Treasury Stock, Value, Acquired, Cost Method, excluding Commissions	$ 27,288
Stock Repurchase Program, Cost Incurred	$ 22
February 2018 Share Repurchase Program
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount						$ 175,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 56,134
August 2018 Share Repurchase Program
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount					$ 100,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 100,000
Share Repurchase Programs
Equity, Class of Treasury Stock
Treasury Stock, Shares, Acquired		6,896
Treasury Stock, Value, Acquired, Cost Method, excluding Commissions		$ 118,866
Stock Repurchase Program, Repurchase Accrual		2,675
Stock Repurchase Program, Cost Incurred		$ 97
November 2018 Share Repurchase Program | Subsequent Event
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount				$ 120,000
August and November 2018 Share Repurchase Program | Subsequent Event
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount				$ 220,000
February 2017 Share Repurchase Program
Equity, Class of Treasury Stock
Stock Repurchase Program, Authorized Amount							$ 150,000
Treasury Stock, Shares, Acquired		1,385	6,131
Treasury Stock, Value, Acquired, Cost Method, excluding Commissions		$ 22,633	$ 90,876
Stock Repurchase Program, Repurchase Accrual			899
Stock Repurchase Program, Cost Incurred		$ 19	$ 88