Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Ordinary Shares	Treasury Shares	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance (in shares) at Dec. 31, 2017		178,437	(7,076)
Beginning Balance at Dec. 31, 2017	$ 2,345,626	$ 2,289	$ (288,478)	$ 1,663,367	$ 1,031,612	$ (63,164)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised (in shares)			58
Stock options exercised	2,219		$ 2,250	126	(157)
Retirement of ordinary shares (in shares)		(7,018)	7,018
Retirement of ordinary shares		$ (90)	$ 286,228		(286,138)
Share-based compensation	5,090			5,090
Net income	90,490				90,490
Other comprehensive income (loss)	7,516					7,516
Ending Balance at Mar. 31, 2018	2,450,941	$ 2,199	$ 0	1,668,583	835,807	(55,648)
Ending Balance (in shares) at Mar. 31, 2018		171,419	0
Beginning Balance (in shares) at Dec. 31, 2017		178,437	(7,076)
Beginning Balance at Dec. 31, 2017	2,345,626	$ 2,289	$ (288,478)	1,663,367	1,031,612	(63,164)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	195,778
Ending Balance at Jun. 30, 2018	2,522,807	$ 2,202	$ (60,105)	1,676,172	937,452	(32,914)
Ending Balance (in shares) at Jun. 30, 2018		171,634	(1,137)
Beginning Balance (in shares) at Mar. 31, 2018		171,419	0
Beginning Balance at Mar. 31, 2018	2,450,941	$ 2,199	$ 0	1,668,583	835,807	(55,648)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Surrender of shares for tax withholding (in shares)			(70)
Surrender of shares for tax withholding	(3,641)		$ (3,641)
Stock options exercised (in shares)		30
Stock options exercised	1,178	$ 1		1,177
Vesting of restricted securities (in shares)		255
Vesting of restricted securities		$ 2			(2)
Repurchase of ordinary shares (in shares)			(1,137)
Repurchase of ordinary shares	(60,105)		$ (60,105)
Retirement of ordinary shares (in shares)		(70)	70
Retirement of ordinary shares			$ 3,641		(3,641)
Share-based compensation	6,412			6,412
Net income	105,288				105,288
Other comprehensive income (loss)	22,734					22,734
Ending Balance at Jun. 30, 2018	2,522,807	$ 2,202	$ (60,105)	1,676,172	937,452	(32,914)
Ending Balance (in shares) at Jun. 30, 2018		171,634	(1,137)
Beginning Balance (in shares) at Dec. 31, 2018		171,719	(7,571)
Beginning Balance at Dec. 31, 2018	2,608,434	$ 2,203	$ (399,417)	1,691,190	1,340,636	(26,178)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Surrender of shares for tax withholding (in shares)			(6)
Surrender of shares for tax withholding	(275)		$ (275)
Stock options exercised (in shares)		248
Stock options exercised	5,813	$ 3		5,810
Vesting of restricted securities (in shares)		26
Repurchase of ordinary shares (in shares)			(3,036)
Repurchase of ordinary shares	(150,749)		$ (150,749)
Retirement of ordinary shares (in shares)		(6)	6
Retirement of ordinary shares			$ 275		(275)
Share-based compensation	5,940			5,940
Net income	85,065				85,065
Other comprehensive income (loss)	10,143					10,143
Ending Balance at Mar. 31, 2019	2,564,371	$ 2,206	$ (550,166)	1,702,940	1,425,426	(16,035)
Ending Balance (in shares) at Mar. 31, 2019		171,987	(10,607)
Beginning Balance (in shares) at Dec. 31, 2018		171,719	(7,571)
Beginning Balance at Dec. 31, 2018	2,608,434	$ 2,203	$ (399,417)	1,691,190	1,340,636	(26,178)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	158,501
Ending Balance at Jun. 30, 2019	2,617,063	$ 2,209	$ (567,615)	1,710,711	1,492,356	(20,598)
Ending Balance (in shares) at Jun. 30, 2019		172,325	(10,986)
Beginning Balance (in shares) at Mar. 31, 2019		171,987	(10,607)
Beginning Balance at Mar. 31, 2019	2,564,371	$ 2,206	$ (550,166)	1,702,940	1,425,426	(16,035)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Surrender of shares for tax withholding (in shares)			(138)
Surrender of shares for tax withholding	(6,503)		$ (6,503)
Stock options exercised (in shares)		64
Stock options exercised	1,286			1,286
Vesting of restricted securities (in shares)		412
Vesting of restricted securities	0	$ 5			(5)
Repurchase of ordinary shares (in shares)			(379)
Repurchase of ordinary shares	(17,449)		$ (17,449)
Retirement of ordinary shares (in shares)		(138)	138
Retirement of ordinary shares	0	$ (2)	$ 6,503		(6,501)
Share-based compensation	6,485			6,485
Net income	73,436				73,436
Other comprehensive income (loss)	(4,563)					(4,563)
Ending Balance at Jun. 30, 2019	$ 2,617,063	$ 2,209	$ (567,615)	$ 1,710,711	$ 1,492,356	$ (20,598)
Ending Balance (in shares) at Jun. 30, 2019		172,325	(10,986)