Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Common Stock	Additional-Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Income/(Loss)
Beginning Balance (in shares) at Dec. 31, 2018			132,655,941
Beginning Balance at Dec. 31, 2018		$ 1,238,358	$ 1,327	$ 897,544	$ 356,418	$ (16,931)
Net income		103,555			103,555
Other comprehensive income (loss), net of tax		(6,805)				(6,805)
Issuance of common stock under employee plans (in shares)			1,608,832
Issuance of common stock under employee plans, including tax benefits		25,823	$ 16	25,807
Stock-based compensation		37,484		37,484
Repurchase of common stock (in shares)			(3,205,676)
Repurchase of common stock		(137,171)	$ (32)	(21,714)	(115,425)
Dividends paid	[1]	(99,083)			(99,083)
Ending Balance (in shares) at Sep. 30, 2019			131,059,097
Ending Balance at Sep. 30, 2019		1,162,161	$ 1,311	939,121	245,465	(23,736)
Beginning Balance (in shares) at Jun. 30, 2019			131,884,775
Beginning Balance at Jun. 30, 2019		1,174,574	$ 1,319	924,801	264,484	(16,030)
Net income		51,644			51,644
Other comprehensive income (loss), net of tax		(7,706)				(7,706)
Issuance of common stock under employee plans (in shares)			230,400
Issuance of common stock under employee plans, including tax benefits		8,178	$ 3	8,175
Stock-based compensation		13,284		13,284
Repurchase of common stock (in shares)			(1,056,078)
Repurchase of common stock		(44,797)	$ (11)	(7,139)	(37,647)
Dividends paid	[1]	(33,016)			(33,016)
Ending Balance (in shares) at Sep. 30, 2019			131,059,097
Ending Balance at Sep. 30, 2019		$ 1,162,161	$ 1,311	939,121	245,465	(23,736)
Beginning Balance (in shares) at Dec. 31, 2019		130,504,535	130,504,535
Beginning Balance at Dec. 31, 2019		$ 1,176,350	$ 1,305	953,578	242,537	(21,070)
Net income		138,923			138,923
Other comprehensive income (loss), net of tax		(1,670)				(1,670)
Issuance of common stock under employee plans (in shares)			1,855,806
Issuance of common stock under employee plans, including tax benefits		24,971	$ 18	24,953
Stock-based compensation		42,264		42,264
Repurchase of common stock (in shares)			(1,114,701)
Repurchase of common stock		(39,244)	$ (11)	(8,139)	(31,094)
Dividends paid	[1]	$ (102,396)			(102,396)
Ending Balance (in shares) at Sep. 30, 2020		131,245,640	131,245,640
Ending Balance at Sep. 30, 2020		$ 1,239,198	$ 1,312	1,012,656	247,970	(22,740)
Beginning Balance (in shares) at Jun. 30, 2020			131,436,108
Beginning Balance at Jun. 30, 2020		1,269,639	$ 1,314	993,058	299,132	(23,865)
Net income		(4,622)			(4,622)
Other comprehensive income (loss), net of tax		1,125				1,125
Issuance of common stock under employee plans (in shares)			256,034
Issuance of common stock under employee plans, including tax benefits		7,717	$ 2	7,715
Stock-based compensation		15,142		15,142
Repurchase of common stock (in shares)			(446,502)
Repurchase of common stock		(15,563)	$ (4)	(3,259)	(12,300)
Dividends paid	[1]	$ (34,240)			(34,240)
Ending Balance (in shares) at Sep. 30, 2020		131,245,640	131,245,640
Ending Balance at Sep. 30, 2020		$ 1,239,198	$ 1,312	$ 1,012,656	$ 247,970	$ (22,740)

[1] Cash dividends declared per share of common stock were $0.25 for the three months ended September 30, 2019, and $0.75 for the nine months ended September 30, 2019.