Sch II - Condensed Financial Information on Registrant Notes - Dividends, debt and income taxes (Details) - Parent Company - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries (eliminated in consolidation)	$ 91,300	$ 91,997	$ 71,500
Dividends in form of cash
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries (eliminated in consolidation)	$ 91,300	$ 91,997	$ 71,500

This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

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