Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions		Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning Balance at Dec. 31, 2017		$ 1,588.9	$ 1.7	$ 0.1	$ 789.6	$ 795.7	$ 1.7	$ 3.5
Beginning Balance, Shares at Dec. 31, 2017				54,355,535
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201409Member
Net issuance under stock-based plans		$ (11.1)			(11.1)
Net issuance under stock-based plans, shares				502,150
Stock-based compensation		27.3			27.3
Stock repurchase		(75.0)			(11.9)	(63.1)
Stock repurchase, Shares				(818,131)
Cash dividend		(42.4)				(42.4)
Comprehensive income (net of tax):
Net income		392.9				392.9
Other comprehensive income (loss)		(9.1)						(9.1)
Ending Balance at Dec. 31, 2018		1,873.2		$ 0.1	793.9	1,084.8		(5.6)
Ending Balance, Shares at Dec. 31, 2018				54,039,554
Net issuance under stock-based plans		(11.0)			(11.0)
Net issuance under stock-based plans, shares				556,629
Settlement of share-based compensation awards	[1]	30.6			30.6
Stock-based compensation		$ 50.3			50.3
Stock repurchase, Shares		0
Cash dividend		$ (43.5)				(43.5)
Stock dividends accrued					0.5	(0.5)
Comprehensive income (net of tax):
Net income		140.4				140.4
Other comprehensive income (loss)		(16.7)						(16.7)
Ending Balance at Dec. 31, 2019		2,023.3		$ 0.1	864.3	1,181.2		(22.3)
Ending Balance, Shares at Dec. 31, 2019				54,596,183
Net issuance under stock-based plans		(20.7)			(20.7)
Net issuance under stock-based plans, shares				600,318
Stock-based compensation		$ 29.6			29.6
Stock repurchase, Shares		0
Cash dividend		$ (44.0)				(44.0)
Comprehensive income (net of tax):
Net income		350.1				350.1
Other comprehensive income (loss)		22.6						22.6
Ending Balance at Dec. 31, 2020		$ 2,360.9		$ 0.1	$ 873.2	$ 1,487.3		$ 0.3
Ending Balance, Shares at Dec. 31, 2020				55,196,501

[1] Represents the vested but unissued portion of Electro Scientific Industries, Inc. (“ESI”) share-based compensation awards as of the acquisition date of February 1, 2019 as described further in Note 12.