Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and contingencies

Schedule of gross reinsurance premiums written by intermediaries

Gross written premium by intermediary	2018		2017		2016
AON Corporation and subsidiaries	26	%	22	%	22	%
Guy Carpenter & Company and subsidiaries	18	%	18	%	18	%
WT Butler and Co. Ltd.	10	%	10	%	8	%
Total	54	%	50	%	48	%

Schedule of net written premiums by geographic region

(Millions)	2018		2017		2016
United States	$	794.7	$	563.1	$	463.0
Europe		276.5		262.3		258.9
Canada, the Caribbean, Bermuda and Latin America		103.6		111.4		88.3
Asia and Other		182.3		153.4		127.9
Total	$	1,357.1	$	1,090.2	$	938.1

Schedule of future annual minimum rental payments required under non cancellable leases for office space

	Future
(Millions)	Payments
2019	$	10.4
2020		9.2
2021		7.6
2022		6.8
2023 and after		6.1
Total	$	40.1