Debt - Additional Information (Detail)	12 Months Ended
Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Aggregate of long term debt maturing, 2019	$ 17,000,000
Aggregate of long term debt maturing, 2020	605,000,000
Aggregate of long term debt maturing, 2021	846,000,000
Aggregate of long term debt maturing, 2022	1,300,000,000
Aggregate of long term debt maturing, 2023	1,300,000,000
Aggregate of long term debt maturing, Thereafter	7,400,000,000
Diamond Offshore [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	950,000,000
CNA Financial [Member]
Debt Instrument [Line Items]
Acquisition of FHLBC stock	5,000,000
Outstanding borrowings	0
Additional liquidity	$ 111,000,000
CNA Financial [Member] \| 7.0% Notes Due 2018 [Member]
Debt Instrument [Line Items]
Percentage of outstanding aggregate principal amount retired	7.00%
Debt instrument principal amount	$ 150,000,000
CNA Financial [Member] \| Variable Rate Note Due 2036 [Member]
Debt Instrument [Line Items]
Debt instrument principal amount	30,000,000
Senior Unsecured Revolving Credit Facility [Member] \| CNA Financial [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 250,000,000
Senior unsecured revolving credit facility, term	5 years
Revolving Credit Facility [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 325,000,000
Revolving credit facility expiration period	5 years
Debt maturity date	Oct. 02, 2023
Borrowings outstanding amount	$ 0
Revolving Credit Facility [Member] \| Diamond Offshore [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 40,000,000
Revolving credit facility maturity period	2019-03
Revolving Credit Facility [Member] \| Diamond Offshore [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 60,000,000
Revolving credit facility maturity period	2019-10
Revolving Credit Facility [Member] \| Diamond Offshore [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 225,000,000
Revolving credit facility maturity period	2020-10
Revolving Credit Facility [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 1,500,000,000
Debt maturity date	May 26, 2022
Borrowings outstanding amount	$ 580,000,000
Swing Line Subfacility [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	100,000,000
Letter Of Credit Subfacility [Member] \| Diamond Offshore [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 250,000,000
Senior Notes Credit Facility [Member] \| Boardwalk Pipeline [Member]
Debt Instrument [Line Items]
Percentage of outstanding aggregate principal amount retired	5.20%
Debt instrument principal amount	$ 185,000,000
ABL Facility [Member] \| Consolidated Container [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 125,000,000
Debt maturity date	May 23, 2022
Borrowings outstanding amount	$ 9,000,000

Debt Instrument Redemption Amount

No definition available.

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- Definition

Federal Home Loan Bank Borrowing Amount Outstanding

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No definition available.

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- Definition

Line of credit facility extended maturity month and year.

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No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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- Definition

Percentage of principal amount of debt redeemed.

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No definition available.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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- Definition

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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- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Fair value of the amount outstanding under the credit facility.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

Amount of cash outflow to acquire Federal Home Loan Bank (FHLB) stock.

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