Non-Qualified Deferred Compensation Plan (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Securities	$ 35,254	$ 31,351
Deferred compensation obligation	$ 35,137	$ 31,166

Carrying amount as of the balance sheet date of assets held under deferred compensation agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DeferredCompensationPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant