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Borrowings - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Outstanding Balance	$ 200,000
Interest Expense, Debt	10,300	$ 10,500	$ 10,600
Revolving credit agreement
Debt Instrument [Line Items]
Outstanding Balance	$ 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	$ 207,700
Series D | Senior notes
Debt Instrument [Line Items]
Interest Rate Per Annum	4.29%
Outstanding Balance	$ 60,000

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

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