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		51,912			51,912
Other comprehensive income (loss), net of tax		901				901
Issuance of common stock under employee plans (in shares)			1,378,432
Issuance of common stock under employee plans, including tax benefits		17,645	$ 14	17,631
Stock-based compensation		24,200		24,200
Repurchase of common stock (in shares)			(2,149,598)
Repurchase of common stock		(92,375)	$ (22)	(14,574)	(77,779)
Dividends paid	[1]	(66,067)			(66,067)
Ending Balance (in shares) at Jun. 30, 2019			131,884,775
Ending Balance at Jun. 30, 2019		1,174,574	$ 1,319	924,801	264,484	(16,030)
Beginning Balance (in shares) at Mar. 31, 2019			131,866,173
Beginning Balance at Mar. 31, 2019		1,201,253	$ 1,319	910,602	307,153	(17,821)
Net income		28,692			28,692
Other comprehensive income (loss), net of tax		1,791				1,791
Issuance of common stock under employee plans (in shares)			1,133,102
Issuance of common stock under employee plans, including tax benefits		8,431	$ 11	8,420
Stock-based compensation		13,335		13,335
Repurchase of common stock (in shares)			(1,114,500)
Repurchase of common stock		(45,971)	$ (11)	(7,556)	(38,404)
Dividends paid	[1]	(32,957)			(32,957)
Ending Balance (in shares) at Jun. 30, 2019			131,884,775
Ending Balance at Jun. 30, 2019		$ 1,174,574	$ 1,319	924,801	264,484	(16,030)
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		143,544			143,544
Other comprehensive income (loss), net of tax		(2,795)				(2,795)
Issuance of common stock under employee plans (in shares)			1,599,772
Issuance of common stock under employee plans, including tax benefits		17,252	$ 16	17,236
Stock-based compensation		27,124		27,124
Repurchase of common stock (in shares)			(668,199)
Repurchase of common stock		(23,680)	$ (7)	(4,880)	(18,793)
Dividends paid	[1]	$ (68,156)			(68,156)
Ending Balance (in shares) at Jun. 30, 2020		131,436,108	131,436,108
Ending Balance at Jun. 30, 2020		$ 1,269,639	$ 1,314	993,058	299,132	(23,865)
Beginning Balance (in shares) at Mar. 31, 2020			130,595,203
Beginning Balance at Mar. 31, 2020		1,280,117	$ 1,306	973,354	335,876	(30,419)
Net income		10,889			10,889
Other comprehensive income (loss), net of tax		6,554				6,554
Issuance of common stock under employee plans (in shares)			1,344,231
Issuance of common stock under employee plans, including tax benefits		8,261	$ 13	8,248
Stock-based compensation		15,130		15,130
Repurchase of common stock (in shares)			(503,326)
Repurchase of common stock		(17,153)	$ (5)	(3,674)	(13,474)
Dividends paid	[1]	$ (34,159)			(34,159)
Ending Balance (in shares) at Jun. 30, 2020		131,436,108	131,436,108
Ending Balance at Jun. 30, 2020		$ 1,269,639	$ 1,314	$ 993,058	$ 299,132	$ (23,865)

[1] Cash dividends declared per share of common stock were $0.25 for the three months ended June 30, 2019, and $0.50 for the six months ended June 30, 2019.