Income Taxes (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Statutory Rate [Line Items]
Deferred Income Tax Expense (Benefit)	$ (8,948)	$ 6,156	$ (6,889)
Analysis of effective income tax rate for continuing operations
U.S. state and local income tax, net	51,207	54,777	44,885
Non-deductible expenses in the U.S.	(236)	525	737
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	188	(255)	(165)
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	168	182	221
Bermuda | Foreign Tax Authority
Analysis of effective income tax rate for continuing operations
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(21,517)	(31,250)	(20,789)
Ireland | Foreign Tax Authority
Analysis of effective income tax rate for continuing operations
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(2,348)	(276)	(3,073)
SINGAPORE
Income Tax Statutory Rate [Line Items]
Deferred Income Tax Expense (Benefit)	4,063
SINGAPORE | Foreign Tax Authority
Analysis of effective income tax rate for continuing operations
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(15,839)	(7,519)	(5,650)
Other low tax jurisdictions | Foreign Tax Authority
Analysis of effective income tax rate for continuing operations
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(5,581)	$ (3,877)	$ (3,395)
UNITED STATES
Income Tax Statutory Rate [Line Items]
Deferred Income Tax Expense (Benefit)	$ 2,779