Junior Subordinated Deferrable Interest Debentures (Key Information) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Junior subordinated interest deferrable debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 134,642	$ 134,642
Trust VIII
Junior subordinated interest deferrable debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 25,774
Interest rate (as a percent)	3.29%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	3.05%
Trust IX
Junior subordinated interest deferrable debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 41,238
Interest rate (as a percent)	1.85%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.62%
Trust X
Junior subordinated interest deferrable debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 21,021
Interest rate (as a percent)	1.86%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.65%
Trust XI
Junior subordinated interest deferrable debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 25,990
Interest rate (as a percent)	1.85%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.62%
Trust XII
Junior subordinated interest deferrable debentures, major types of business trusts
Junior subordinated deferrable interest debentures	$ 20,619
Interest rate (as a percent)	1.68%
Interest rate index	LIBOR
Spread on interest rate index (as a percent)	1.45%

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

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- Definition

The average effective interest rate during the reporting period.

+ References

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-Publisher FASB
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-Topic 835
-SubTopic 30
-Section 45
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- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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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.

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- Definition

Including the current and noncurrent portions, the carrying value of junior subordinated long-term debt owed to unconsolidated subsidiary trusts as of the balance sheet date. Such debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets and was initially scheduled to be repaid after one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
-Paragraph 1
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