Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

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Amount of right to receive securities collateral under master netting arrangements that have not been offset against derivative liabilities.

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Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

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Dividends received on equity and other investments during the current period.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Indebtedness divided by net capital.

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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Condensed Financial Information of Registrant Condensed Financial Information of Registrant (Narratives) (Details) $ in Thousands				1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 29, 2017 USD ($)	Mar. 08, 2017 USD ($)	Aug. 09, 2013	Jan. 31, 2017	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jul. 31, 2018	Jan. 31, 2018	Jul. 07, 2017
Condensed Financial Statements, Captions [Line Items]
Proceeds from special purpose investment vehicles					$ 5,200	$ 6,000
Proceeds from dividends received						135,000	$ 109,000	$ 111,000
Repayments of debt		$ 320,000
Swap [Member] \| AFL [Member]
Condensed Financial Statements, Captions [Line Items]
Swap agreement collateral						40,000
Notional amount								$ 152,000
Term of swap agreement			3 years	1 year
Swap [Member] \| AFL [Member] \| LIBOR [Member]
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate			1.35%					1.35%			1.28%
Swap [Member] \| FFL [Member]
Condensed Financial Statements, Captions [Line Items]
Swap agreement collateral						31,000
Notional amount						100,000	$ 100,000
Term of swap agreement							1 year
Swap [Member] \| FFL [Member] \| LIBOR [Member]
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate							1.28%		1.05%	1.20%
Unsecured Notes One [Member] \| Unsecured Debt [Member]
Condensed Financial Statements, Captions [Line Items]
Unsecured debt						$ 375,000
Interest rate, stated percentage		4.40%				4.40%
Debt issuance costs		$ 3,400
Discount percent		99.847%
Interest rate, effective percentage		4.45%
Unsecured Notes Two [Member] \| Revolving Credit Facility [Member]
Condensed Financial Statements, Captions [Line Items]
Loan maximum borrowing capacity	$ 50,000
Unsecured Notes Two [Member] \| Unsecured Debt [Member]
Condensed Financial Statements, Captions [Line Items]
Unsecured debt						$ 0
Minimum [Member] \| Revolving Credit Facility [Member]
Condensed Financial Statements, Captions [Line Items]
Debt to total capital ratio	0.15
Commitment fee on undrawn portion of facility	0.125%
Minimum [Member] \| LIBOR [Member] \| Revolving Credit Facility [Member]
Condensed Financial Statements, Captions [Line Items]
Revolving credit facility term	5 years
Basis spread on variable rate	1.125%
Debt to total capital ratio	0.15
Minimum [Member] \| Unsecured Notes Two [Member] \| Revolving Credit Facility [Member]
Condensed Financial Statements, Captions [Line Items]
Commitment fee on undrawn portion of facility						0.15%
Minimum [Member] \| Unsecured Notes Two [Member] \| Unsecured Debt [Member] \| LIBOR [Member]
Condensed Financial Statements, Captions [Line Items]
Basis spread on variable rate						0.1125%