Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Ordinary Shares Issued	Accumulated Other Comprehensive Income	Retained Earnings (Accumulated Deficit)	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Accumulated Other Comprehensive Income	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings (Accumulated Deficit)
Balance at Dec. 31, 2017	$ 6,170.5	$ 7,892.9	$ 253.1	$ (1,975.5)	$ 5.2	$ (1.0)	$ 6.2
Balance, shares at Dec. 31, 2017		140,800
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	131.0			131.0
Other comprehensive income (loss)	(167.5)		(167.5)
Issuance of ordinary shares under:
Stock options, shares		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)	$ (3.3)	$ 0.0	$ (3.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	146.1			146.1
Other comprehensive income (loss)	$ 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
Restricted stock plan	0.0
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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(162.6)			(162.6)
Other comprehensive income (loss)	$ 255.6		255.6
Issuance of ordinary shares under:
Stock options, shares	0
Restricted stock plan, shares		600
Restricted stock plan	$ 0.0
Compensation for stock options	2.0	$ 2.0
Compensation for restricted stock	56.5	56.5
Cash dividends	(123.9)	$ (123.9)
Shares withheld for payment of employees' withholding tax liability, shares		(200)
Shares withheld for payment of employees' withholding tax liability	(10.7)	$ (10.7)
Repurchases of ordinary shares, shares		(3,400)
Repurchases of ordinary shares	(164.2)	$ (164.2)
Purchase of subsidiary's minority interest	(1.4)	$ (1.4)
Balance, shares at Dec. 31, 2020		133,100
Balance at Dec. 31, 2020	$ 5,655.1	$ 7,118.2	$ 395.0	$ (1,858.1)