Fair Value Measurements - Summary of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Fixed maturity securities, available-for-sale	$ 1,570,605	$ 1,433,626
Equity securities	71,394	80,735
Bank loan participations	202,888
Bank loan participations		260,864
Cash and cash equivalents	291,223	206,912
Restricted cash equivalents	1,107,321	1,199,164
Liabilities
Senior debt	277,300	158,300
Junior subordinated debt	104,055	104,055
Carrying Value
Assets
Fixed maturity securities, available-for-sale	1,570,605	1,433,626
Equity securities	71,394	80,735
Bank loan participations	202,888
Bank loan participations		260,864
Cash and cash equivalents	291,223	206,912
Restricted cash equivalents	1,107,321	1,199,164
Short-term investments	71,058	156,925
Other invested assets – notes receivable	7,180	13,250
Liabilities
Senior debt	277,300	158,300
Junior subordinated debt	104,055	104,055
Fair Value
Assets
Fixed maturity securities, available-for-sale	1,570,605	1,433,626
Equity securities	71,394	80,735
Bank loan participations	202,888
Bank loan participations		252,423
Cash and cash equivalents	291,223	206,912
Restricted cash equivalents	1,107,321	1,199,164
Short-term investments	71,058	156,925
Other invested assets – notes receivable	11,458	18,756
Liabilities
Senior debt	257,965	158,043
Junior subordinated debt	$ 106,618	$ 122,193

Fair Value, Option, Loans Held as Assets, Aggregate Fair Value

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Represents carrying value of notes receivable as on reporting date.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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Amount of cash equivalents restricted as to withdrawal or usage. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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