Debt Instrument, Covenant, Actual Aggregate Total Adjusted Capital To Company Action Level Risk-Based Capital Ratio

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Debt Instrument, Covenant, Actual Consolidated Net Worth, Amount

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Debt Instrument, Covenant, Actual Debt To Total Capitalization Ratio

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Debt Instrument, Covenant, Maximum Required Debt To Total Capitalization Ratio

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Debt Instrument, Covenant, Minimum Required Aggregate Total Adjusted Capital To Company Action Level Risk-Based Capital Ratio

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Debt Instrument, Covenant, Required Minimum Consolidated Net Worth, Amount

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Debt Instrument, Covenant, Required Minimum Consolidated Net Worth, Component One, Amount

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Debt Instrument, Covenant, Required Minimum Net Worth, Component Two, Percent Of Net Equity Proceeds Received From Issuance And Sale Of Equity Interests

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- Definition

Debt Instrument, Debt Default, Percentage Of Principal Amount Outstanding

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Payment Of Redemption Premium

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

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.

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- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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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.

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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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 borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

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NOTES PAYABLE - DIRECT CORPORATE OBLIGATIONS - NARRATIVE (Details) - USD ($)				3 Months Ended		9 Months Ended
	Jun. 12, 2019	Oct. 13, 2017	May 19, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Outstanding amount				$ 988,700,000		$ 988,700,000		$ 916,800,000
Loss on extinguishment of debt				0	$ 0	7,300,000	$ 0
Repayments of related party debt						6,100,000
Write off of unamortized issuance costs						1,200,000
Line of credit \| Revolving Credit Agreement
Debt Instrument [Line Items]
Line of credit maximum borrowing capacity		$ 250,000,000.0	$ 150,000,000.0
Debt instrument, term			4 years
Initial drawing amount			$ 100,000,000.0
Remaining borrowing capacity		$ 100,000,000.0	$ 50,000,000.0
Outstanding amount				$ 0		$ 0		100,000,000.0
Debt covenant, required minimum debt to total capitalization ratio		35.00%
Debt covenant, actual debt to total capitalization ratio at period end				24.60%		24.60%
Debt covenant, minimum required aggregate total adjusted capital to company action level risk-based capital ratio			250.00%
Debt covenant, actual aggregate total adjusted capital to company action level risk-based capital ratio at period end				405.00%		405.00%
Debt covenant, minimum required consolidated net worth, component one, amount			$ 2,674,000,000
Debt covenant, minimum required consolidated net worth, component two, as a percent of net equity proceeds received from issuance and sale of equity interests			50.00%
Debt covenant, actual consolidated net worth at period end				$ 3,110,400,000		$ 3,110,400,000
Debt covenant, required minimum consolidated net worth, amount				$ 2,689,700,000		$ 2,689,700,000
Line of credit \| Revolving Credit Agreement \| Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Line of credit \| Revolving Credit Agreement \| Eurodollar \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.375%
Line of credit \| Revolving Credit Agreement \| Eurodollar \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		2.125%
Line of credit \| Revolving Credit Agreement \| Base Rate \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		0.375%
Line of credit \| Revolving Credit Agreement \| Base Rate \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		1.125%
5.250% Senior Notes due May 2029 \| Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 500,000,000.0
Interest rate				5.25%		5.25%
Debt default, percentage of principal amount outstanding	50.00%
Outstanding amount				$ 500,000,000.0		$ 500,000,000.0		$ 0
5.250% Senior Notes due May 2029 \| On and after February 28, 2029 \| Senior Notes
Debt Instrument [Line Items]
Redemption price	100.00%
5.250% Senior Notes due May 2029 \| Change of Control Repurchase Event \| Senior Notes
Debt Instrument [Line Items]
Redemption price	101.00%
4.500% Senior Notes due May 2020 \| Senior Notes
Debt Instrument [Line Items]
Interest rate								4.50%
Outstanding amount				$ 0		$ 0		$ 325,000,000.0