Consolidated Statements of Net Proceeds From All Sources (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss)
Other comprehensive income (loss), defined benefit plan, transition asset (obligation), reclassification adjustment from AOCI, tax	$ (101)	$ (24)	$ 84
Net Proceeds From All Sources
Dividends paid - per Sub-share (in dollars per share)	$ 1.75	$ 1.05	$ 0.35
Special dividends paid per Sub-share Certificate (in dollars per share)	$ 4.25	$ 3.00	$ 1.00

Amount of tax expense (benefit) for reclassification adjustment from accumulated other comprehensive income (loss) for transition asset (obligation) of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=118930883&loc=d3e640-108580

Name:	us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetTransitionAssetObligationTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration