Investments - Schedule of unobservable inputs (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Corporate bonds	$ 232,945	$ 83,190
Derivative liabilities (embedded)	6,296	5,563
Significant unobservable inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Corporate bonds	8,333	3,252
Derivative liabilities (embedded)	$ 6,296	5,563
Discounted cash flow | Corporate bonds | Significant unobservable inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Corporate bonds		$ 2,444
Mean Monthly Investment Return	1.20%	1.20%
Credit spreads		9.86%
Duration		3 years
Discounted cash flow | Corporate bonds | Significant unobservable inputs (Level 3) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield		10.40%
Volatility		25.00%
Contractual Variable Annual Investment Credit	0.00%	0.00%
Duration Until Contract Settlement	5 years	5 years
Duration From Valuation Date	3 years 3 months	4 years
Discounted cash flow | Corporate bonds | Significant unobservable inputs (Level 3) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield		11.40%
Volatility		35.00%
Contractual Variable Annual Investment Credit	2.50%	2.50%
Duration Until Contract Settlement	5 years 6 months	5 years 6 months
Duration From Valuation Date	4 years 3 months	5 years
Private Equity Funds | Market Approach Valuation Technique | Significant unobservable inputs (Level 3)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, Fair Value Disclosure	$ 35,185
Private Equity Funds | Market Approach Valuation Technique | Significant unobservable inputs (Level 3) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	10.00%
Private Equity Funds | Market Approach Valuation Technique | Significant unobservable inputs (Level 3) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Discount Rate	25.00%