Fair Value Accounting (Mortgage Loans Held for Sale and Changes in Fair Value Included in Consolidated Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Unpaid principal balance	$ 240,287		$ 210,292
Fair value less aggregate unpaid principal balance	1,723		$ 6,355
Mortgage loans held for sale	$ (4,632)	$ 619

This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of long-term debt instruments that have contractual principal amounts and for which the fair value option has been elected.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

Name:	us-gaap_FairValueOptionAggregateDifferencesLongTermDebtInstruments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant