Fair Value of Financial Instruments - Schedule of Fair Value, Valuation Techniques and Significant Unobservable Inputs for Financial Instruments Categorized as Level 3 (Details) $ in Thousands	Dec. 31, 2020 USD ($) year	Dec. 31, 2019 USD ($) year
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivatives, index options	$ 132,821	$ 157,588
Total assets	10,921,488	3,538,129
Total liabilities	167,553	171,203
Level 3
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivatives, index options	132,821	157,588
Total assets	132,821	157,588
Contingent consideration on businesses acquired	0	4,076
Total liabilities	167,553	171,203
Level 3 | Broker prices
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivatives, index options	132,821	157,588
Level 3 | Deterministic cash flow model
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Policyholder account balances	161,351	155,902
Level 3 | Black-Scholes model
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Share based compensation	$ 6,202	11,225
Level 3 | Probabilistic Method
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contingent consideration on businesses acquired		$ 4,076
Implied volatility | Level 3 | Broker prices | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivatives, index options, measurement input	0.1296	0.1310
Implied volatility | Level 3 | Broker prices | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivatives, index options, measurement input	0.5369	0.1990
Implied volatility | Level 3 | Broker prices | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivatives, index options, measurement input	0.2070	0.1525
Projected option cost | Level 3 | Deterministic cash flow model | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Policyholder account balances, measurement input	0.000	0.000
Projected option cost | Level 3 | Deterministic cash flow model | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Policyholder account balances, measurement input	0.4504	0.1755
Projected option cost | Level 3 | Deterministic cash flow model | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Policyholder account balances, measurement input	0.0327	0.0314
Expected term | Level 3 | Black-Scholes model | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Share based compensation, measurement input | year	1.0	1.9
Expected term | Level 3 | Black-Scholes model | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Share based compensation, measurement input | year	9.9	10
Expected volatility | Level 3 | Black-Scholes model
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Share based compensation, measurement input	0.3347	0.2219
Discount rate | Level 3 | Probabilistic Method
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contingent consideration on businesses acquired, measurement input		0.100
Projected renewal premium | Level 3 | Probabilistic Method | Minimum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contingent consideration on businesses acquired, measurement input		57,200
Projected renewal premium | Level 3 | Probabilistic Method | Maximum
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contingent consideration on businesses acquired, measurement input		82,400
Projected renewal premium | Level 3 | Probabilistic Method | Weighted Average
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Contingent consideration on businesses acquired, measurement input		71,900