Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Ordinary Shares Issued	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)
Balance at Dec. 31, 2015	$ 10,107.4	$ 8,142.6	$ (15.3)	$ 1,980.1
Balance, shares at Dec. 31, 2016		143,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(4,012.8)			(4,012.8)
Other comprehensive loss	(66.5)		(66.5)
Issuance of ordinary shares under:
Stock options, shares		200
Stock options	8.3	$ 8.3
Restricted stock plan, shares		200
Restricted stock plan	0.0
Compensation for stock options	5.0	$ 5.0
Compensation for restricted stock	18.0	18.0
Cash dividends	(83.2)	(20.8)		(62.4)
Tax effect from stock transactions	(1.5)	$ (1.5)
Shares withheld for payment of employees' withholding tax liability, shares		(100)
Shares withheld for payment of employees' withholding tax liability	(6.3)	$ (6.3)
Repurchases of ordinary shares	(10.3)	$ (10.3)
Balance, shares at Dec. 31, 2015		143,100
Balance at Dec. 31, 2016	5,958.1	$ 8,135.0	(81.8)	(2,095.1)
Balance, shares at Dec. 31, 2017		140,800
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	119.6			119.6
Other comprehensive loss	$ 334.9		334.9
Issuance of ordinary shares under:
Stock options, shares	31	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)
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, 2016		143,400
Balance at Dec. 31, 2017	6,170.5	$ 7,892.9	253.1	(1,975.5)
Issuance of ordinary shares under:
ASU adoption impact | Adjustments for New Accounting Pronouncements	5.2		(1.0)	6.2
Balance, shares at Dec. 31, 2018		135,900
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	131.0			131.0
Other comprehensive loss	$ (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
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, 2017		140,800
Balance at Dec. 31, 2018	$ 5,668.0	$ 7,421.7	$ 84.6	$ (1,838.3)