Taxation - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Line Items]
Deferred tax asset, per balance sheet	$ 310,542	$ 282,311
Deferred tax liability, per balance sheet	77,271	120,651
Valuation allowance	367,366	276,301
Increase (decrease) in valuation allowance, amount	91,100
Capital loss valuation allowance, amount	89,600
Capital loss carryforwards, tax effected	71,651	5,047
Capital loss carryforwards available	293,500
Net operating loss carryforwards, amount	1,600,000
Net operating loss	323,716	181,295
Net operating loss carryforwards valuation allowance, amount	206,600
Net operating loss carryforwards, tax effected	117,100
Net realized capital losses	89,568	98,756
Excess tax benefits on share-based compensation	10,600	9,200
Unrecognized tax benefits	97,780	80,590	$ 37,190	$ 30,000
Accrued interest and penalties	900	400	$ 400
United States
Income Tax Disclosure [Line Items]
Valuation allowance	92,999	106,624
Capital loss valuation allowance, amount	57,900
Capital loss carryforwards available	165,500
Net operating loss carryforwards, amount	108,000
Net operating loss	37,800
Net operating loss carryforwards valuation allowance, amount	800
Net operating loss carryforwards, tax effected	37,000
Net realized capital losses	57,900
United States | Deferred tax asset restricted under Internal Revenue Code Section 382
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, amount	47,000
United States | Carryforwards expiring In 2018
Income Tax Disclosure [Line Items]
Capital loss carryforwards available	59,100
United States | Expiring in future years
Income Tax Disclosure [Line Items]
Capital loss carryforwards available	106,300
United States | Alternative minimum tax
Income Tax Disclosure [Line Items]
Capital loss carryforwards, tax effected	32,300
United States | Foreign tax credit
Income Tax Disclosure [Line Items]
Capital loss carryforwards, tax effected	5,600
United States | Research and development tax credit
Income Tax Disclosure [Line Items]
Capital loss carryforwards, tax effected	3,100
Ireland
Income Tax Disclosure [Line Items]
Valuation allowance	96,642	93,396
Capital loss valuation allowance, amount	30,500
Capital loss carryforwards available	122,100
Net operating loss carryforwards, amount	484,900
Net operating loss	60,600
Net operating loss carryforwards valuation allowance, amount	60,600
Net realized capital losses	30,500
Other jurisdictions
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, amount	629,100
Net operating loss	162,600
Net operating loss carryforwards valuation allowance, amount	104,100
Net operating loss carryforwards, tax effected	58,500
Other jurisdictions | No expiration date
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, amount	609,100
United Kingdom
Income Tax Disclosure [Line Items]
Valuation allowance	32,528	46,732
Capital loss valuation allowance, amount	1,100
Capital loss carryforwards available	5,900
Net operating loss carryforwards, amount	203,300
Net operating loss	39,000
Net operating loss carryforwards valuation allowance, amount	26,200
Net operating loss carryforwards, tax effected	12,800
Net realized capital losses	1,100
United Kingdom | Foreign tax credit
Income Tax Disclosure [Line Items]
Capital loss carryforwards, tax effected	30,700
Switzerland
Income Tax Disclosure [Line Items]
Valuation allowance	15,025	$ 7,818
Net operating loss carryforwards, amount	200,100
Net operating loss	23,700
Net operating loss carryforwards valuation allowance, amount	14,900
Net operating loss carryforwards, tax effected	8,800
Switzerland | Carryforwards Expiring in Next Fiscal Year [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, amount	5,300
Switzerland | Carryforwards expiring In 2018
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, amount	4,000
Switzerland | Expiring in future years
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, amount	$ 190,800