Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions		3 Months Ended
Jan. 31, 2018	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Special dividend declared in December 2017 and paid in January 2018	$ 269.2
Special dividend paid in September 2019		$ 303.4

Special dividend declared in December 2017 and paid in January 2018, amount

No definition available.

Name:	ori_SpecialDividendDeclaredInDecember2017AndPaidInJanuary2018Amount
Namespace Prefix:	ori_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration