Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Ordinary Shares Issued	Accumulated Other Comprehensive Income	Retained Earnings (Accumulated Deficit)
Balance at Dec. 31, 2016	$ 5,958.1	$ 8,135.0	$ (81.8)	$ (2,095.1)
Balance, shares at Dec. 31, 2016		143,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	119.6			119.6
Other comprehensive income	334.9		334.9
Issuance of ordinary shares under:
Stock options, shares		100
Stock options	0.7	$ 0.7
Restricted stock plan, shares		100
Restricted stock plan	0.0
Compensation for stock options	8.9	$ 8.9
Compensation for restricted stock	34.9	34.9
Cash dividends	(91.1)	$ (91.1)		0.0
Shares withheld for payment of employees' withholding tax liability, shares		(100)
Shares withheld for payment of employees' withholding tax liability	(4.0)	$ (4.0)
Repurchases of ordinary shares, shares		(2,700)
Repurchases of ordinary shares	(191.5)	$ (191.5)
Balance, shares at Dec. 31, 2017		140,800
Balance at Dec. 31, 2017	6,170.5	$ 7,892.9	253.1	(1,975.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	131.0			131.0
Other comprehensive income	$ (167.5)		(167.5)
Issuance of ordinary shares under:
Stock options, shares	33	100
Stock options	$ 1.3	$ 1.3
Restricted stock plan, shares		200
Restricted stock plan	0.0
Compensation for stock options	8.1	$ 8.1
Compensation for restricted stock	29.6	29.6
Cash dividends	(104.9)	$ (104.9)
Shares withheld for payment of employees' withholding tax liability, shares		(100)
Shares withheld for payment of employees' withholding tax liability	(5.3)	$ (5.3)
Repurchases of ordinary shares, shares		(5,100)
Repurchases of ordinary shares	(400.0)	$ (400.0)
Balance, shares at Dec. 31, 2018		135,900
Balance at Dec. 31, 2018	5,668.0	$ 7,421.7	84.6	(1,838.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	146.1			146.1
Other comprehensive income	$ 54.8		54.8
Issuance of ordinary shares under:
Stock options, shares	27	0
Stock options	$ 0.9	$ 0.9
Restricted stock plan, shares		300
Compensation for stock options	4.7	$ 4.7
Compensation for restricted stock	50.6	50.6
Cash dividends	(112.4)	$ (112.4)
Shares withheld for payment of employees' withholding tax liability, shares		(100)
Shares withheld for payment of employees' withholding tax liability	(5.6)	$ (5.6)
Repurchases of ordinary shares, shares		0
Balance, shares at Dec. 31, 2019		136,100
Balance at Dec. 31, 2019	$ 5,803.8	$ 7,359.9	$ 139.4	$ (1,695.5)