Employee Deferred Compensation Plan Obligations - Compensation Expense Related to Qualified and Nonqualified Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred Compensation Plans [Abstract]
Contribution expense	$ 42,092	$ 26,122	$ 24,184
Employee deferred compensation expense (income) related to changes in the fair value of trust assets	75,188	54,917	(11,486)
Total compensation expense related to qualified defined contribution plans and nonqualified plans	$ 117,280	$ 81,039	$ 12,698

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 30
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration