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Significant Accounting Policies - Investment Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Company's matching contribution, percentage	6.00%
Discretionary contributions to the Plan, amount	$ 0	$ 0	$ 0
Total payment and cost to the Plan	$ 2,976,000	$ 3,460,000	$ 3,205,000
Minimum
Defined Contribution Plan Disclosure [Line Items]
Discretionary contributions to the Plan, percentage	1.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Discretionary contributions to the Plan, percentage	6.00%

X

- Definition

Defined Contribution Plan, Employer Discretionary Contribution Percent

+ References

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- Definition

Amount of cost for defined contribution plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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- Definition

Amount of discretionary contributions made by an employer to a defined contribution plan.

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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

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