Taxation - Reconciliation of effective tax rate (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Expected tax provision at weighted average rate	$ 132,775	$ 43,092	$ 53,358
Permanent differences:
Non taxable (income) loss	(19,870)	(50,745)	(42,428)
Prior year adjustments	5,990	6,067	(622)
Prior year adjustments on completion of IRS examinations	0	0	(19,192)
State, local and foreign taxes	47,078	12,225	18,312
Valuation allowance	(181)	5,754	(16,644)
Net allocated investment income	3,399	5,949	41,727
Stock options	411	1,501	4,749
Non-deductible expenses	22,556	23,662	16,145
Realized capital loss carry-forward valuation allowance reduction	(2,916)	0	(24,473)
Adjustments related to Life Retro Arrangements	(99,535)	0	0
Non-taxable reserve release	0	0	3,096
Uncertain tax positions	7,190	30,000	0
Total Tax Expense	$ 96,897us-gaap_IncomeTaxExpenseBenefit	$ 77,505us-gaap_IncomeTaxExpenseBenefit	$ 34,028us-gaap_IncomeTaxExpenseBenefit

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

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-Name Accounting Standards Codification

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The portion of the difference between total income tax expense (benefit) as reported in the Income Statement and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to allocated investment income.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to reserve releases.

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