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Borrowings - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 100,000
Outstanding Balance	200,000	$ 200,000
Interest Expense, Debt	10,500	10,600	$ 10,900
Revolving credit agreement
Debt Instrument [Line Items]
Outstanding Balance	$ 0	0
Commitment fee percentage	0.175%
Revolving credit agreement | Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.175%
Revolving credit agreement | Maximum
Debt Instrument [Line Items]
Commitment fee percentage	0.50%
Revolving credit agreement | LIBOR adjusted by a statutory reserve percentage | Minimum
Debt Instrument [Line Items]
Spread on variable rate	1.50%
Revolving credit agreement | LIBOR adjusted by a statutory reserve percentage | Maximum
Debt Instrument [Line Items]
Spread on variable rate	2.50%
Revolving credit agreement | Federal funds effective rate
Debt Instrument [Line Items]
Spread on variable rate	0.50%
Revolving credit agreement | One-month LIBOR adjusted by a statutory reserve percentage
Debt Instrument [Line Items]
Spread on variable rate	1.00%
Revolving credit agreement | Margin based on leverage ratio | Minimum
Debt Instrument [Line Items]
Spread on variable rate	0.50%
Revolving credit agreement | Margin based on leverage ratio | Maximum
Debt Instrument [Line Items]
Spread on variable rate	1.50%
Level 2 | Recurring
Debt Instrument [Line Items]
Borrowings	$ 202,800
Series D | Senior notes
Debt Instrument [Line Items]
Interest Rate Per Annum	4.29%
Outstanding Balance	$ 60,000	$ 60,000	$ 60,000
Series A | Senior notes
Debt Instrument [Line Items]
Interest Rate Per Annum			4.98%

X

- Definition

Amount of short-term and long-term debt and lease obligation.

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

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

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

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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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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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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