Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Detail) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	$ 3,037
Financial assets:
Short term investments	586	$ 653
Other investments	363	478
Derivative assets	89	75
Other assets	3	3
Long-term Debt	2,760	2,822
Financial liabilities:
Derivative liabilities	138	90
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	2,928	3,121
Financial assets:
Loans	2,932	3,108
Derivative assets	62	52
Long-term Debt	4,263	4,554
Financial liabilities:
Derivative liabilities	1,610	1,657
Long-term debt	4,092	4,351
Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	586	653
Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	2,806	2,957
Municipal Bonds [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	122	164
Total Fair Value [Member]
Financial assets:
Cash	89	79
Reported Value Measurement [Member]
Financial assets:
Cash	89	79
Loans	10
Other assets	3	3
Total financial assets	9,513	10,242
Financial liabilities:
Liabilities for net financial guarantees written	(763)	(863)
Long-term debt	3,217	3,262
Total financial liabilities	8,464	8,699
Reported Value Measurement [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	2	2
Loans	2,932	3,108
Financial liabilities:
Long-term debt	4,263	4,554
Reported Value Measurement [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	586	653
Reported Value Measurement [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	363	478
Reported Value Measurement [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	2,806	2,957
Reported Value Measurement [Member] | Municipal Bonds [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	122	164
Reported Value Measurement [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	1
Derivative liabilities	136	89
Reported Value Measurement [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial liabilities:
Derivative liabilities	1,610	1,657
Reported Value Measurement [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Derivative assets	62	52
Reported Value Measurement [Member] | Other Credit Derivatives [Member]
Financial liabilities:
Derivative liabilities	2
Other Assets [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	89	75
Interest Rate Swaps - Liability Position [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative Asset, Fair Value, Gross Liability	1
Level 1 [Member]
Financial assets:
Cash	86	70
Total financial assets	1,004	1,091
Financial liabilities:
Liabilities for net financial guarantees written	0	0
Long-term debt	0	0
Total financial liabilities	0	0
Level 1 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	2	2
Loans	0	0
Financial liabilities:
Long-term debt	0	0
Level 1 [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	528	598
Level 1 [Member] | Equity Method Investments [Member]
Financial assets:
Other assets	0	0
Level 1 [Member] | Loans Receivable [Member]
Financial assets:
Loans	0
Level 1 [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	84	136
Level 1 [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Level 1 [Member] | Municipal Bonds [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Level 1 [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	0
Derivative liabilities	0	0
Level 1 [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 1 [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Derivative assets	0	0
Level 1 [Member] | Other Credit Derivatives [Member]
Financial assets:
Derivative assets	0
Financial liabilities:
Derivative liabilities	0
Level 1 [Member] | Other Assets [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	0	0
Level 1 [Member] | Interest Rate Swaps - Liability Position [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative Asset, Fair Value, Gross Liability	0
Level 2 [Member]
Financial assets:
Cash	3	9
Total financial assets	2,335	2,593
Financial liabilities:
Liabilities for net financial guarantees written	0	0
Long-term debt	2,584	2,829
Total financial liabilities	8,444	8,983
Level 2 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	0	0
Loans	0	0
Financial liabilities:
Long-term debt	4,115	4,408
Level 2 [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	57	55
Level 2 [Member] | Equity Method Investments [Member]
Financial assets:
Other assets	0	0
Level 2 [Member] | Loans Receivable [Member]
Financial assets:
Loans	0
Level 2 [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	0	0
Level 2 [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Level 2 [Member] | Municipal Bonds [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	122	164
Level 2 [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	1
Derivative liabilities	136	89
Level 2 [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial liabilities:
Derivative liabilities	1,610	1,657
Level 2 [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Derivative assets	62	52
Level 2 [Member] | Other Credit Derivatives [Member]
Financial assets:
Derivative assets
Financial liabilities:
Derivative liabilities	0
Level 2 [Member] | Other Assets [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	10	8
Level 2 [Member] | Interest Rate Swaps - Liability Position [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative Asset, Fair Value, Gross Liability	1
Level 3 [Member]
Financial assets:
Cash	0	0
Total financial assets	5,927	6,281
Financial liabilities:
Liabilities for net financial guarantees written	1,057	284
Long-term debt	341	445
Total financial liabilities	1,558	889
Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	0	0
Loans	2,932	3,108
Financial liabilities:
Long-term debt	158	159
Level 3 [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	0	0
Level 3 [Member] | Equity Method Investments [Member]
Financial assets:
Other assets	3	3
Level 3 [Member] | Loans Receivable [Member]
Financial assets:
Loans	11
Level 3 [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	30	61
Level 3 [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	2,806	2,957
Level 3 [Member] | Municipal Bonds [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Level 3 [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	0
Derivative liabilities	0	0
Level 3 [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 3 [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Derivative assets	0	0
Level 3 [Member] | Other Credit Derivatives [Member]
Financial assets:
Derivative assets
Financial liabilities:
Derivative liabilities	2
Level 3 [Member] | Other Assets [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	79	67
Level 3 [Member] | Interest Rate Swaps - Liability Position [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative Asset, Fair Value, Gross Liability	0
Commercial Mortgage Backed Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	51	50
Municipal Bonds [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	218	215
Corporate Debt Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	1,261	1,430
Debt Security, Government, Non-US [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	42	44
US Government Debt Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	177	156
Residential Mortgage-Backed Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	203	248
Collateralized Debt Obligations [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	132	146
Asset-backed Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	283	287
Fair Value, Recurring [Member]
Financial assets:
Total financial assets	9,498	10,260
Financial liabilities:
Liabilities for net financial guarantees written	1,057	284
Long-term debt	2,924	3,274
Total financial liabilities	10,001	9,872
Fair Value, Recurring [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	2	2
Loans	2,932	3,108
Financial liabilities:
Long-term debt	4,274	4,567
Fair Value, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	51	50
Fair Value, Recurring [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	586	653
Fair Value, Recurring [Member] | Equity Method Investments [Member]
Financial assets:
Other assets	3	3
Fair Value, Recurring [Member] | Loans Receivable [Member]
Financial assets:
Loans	11
Fair Value, Recurring [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	345	493
Fair Value, Recurring [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	283	287
Fair Value, Recurring [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	132	146
Fair Value, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	203	248
Fair Value, Recurring [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	177	156
Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	42	44
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	1,261	1,430
Fair Value, Recurring [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	2,806	2,957
Fair Value, Recurring [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	218	215
Fair Value, Recurring [Member] | Municipal Bonds [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	122	164
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	1
Derivative liabilities	136	89
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial liabilities:
Derivative liabilities	1,610	1,657
Fair Value, Recurring [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Financial assets:
Derivative assets	62	52
Fair Value, Recurring [Member] | Other Credit Derivatives [Member]
Financial assets:
Derivative assets	0
Financial liabilities:
Derivative liabilities	2
Fair Value, Recurring [Member] | Other Assets [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	89	75
Fair Value, Recurring [Member] | Interest Rate Swaps - Liability Position [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative Asset, Fair Value, Gross Liability	1
Fair Value, Recurring [Member] | Level 1 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	177	156
Fair Value, Recurring [Member] | Level 1 [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	42	44
Fair Value, Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	51	50
Fair Value, Recurring [Member] | Level 2 [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	217	215
Fair Value, Recurring [Member] | Level 2 [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	132	146
Fair Value, Recurring [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	203	248
Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	1,261	1,430
Fair Value, Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	218	215
Fair Value, Recurring [Member] | Level 3 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	66	72
Fair Value, Recurring [Member] | Level 3 [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0	0
Collateral Pledged [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)		$ 85
Collateral Pledged [Member] | Short-term Investments [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	85
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	85
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	85
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed income securities, at fair value (amortized cost of $2,367 and $2,450)	$ 0