Share Capital - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Preferred stock par value (in usd per share)	$ 0.2		$ 0.2
Liquidation preference per share (in usd per share)	$ 1,000		$ 1,000
Preferred shares lock-up period	5 years
Immediate payment applied from collateral already paid	$ 190.6	$ 0.0
Forward contract
Class of Stock [Line Items]
Strike price (in usd per share)	$ 12.00
Immediate payment applied from collateral already paid	$ 190.6
Net collateral paid balance	$ 66.5		$ 37.8
OppenheimerFunds
Class of Stock [Line Items]
Preferred stock par value (in usd per share)	$ 0.20
Liquidation preference per share (in usd per share)	$ 1,000
Preferred shares dividend rate (percent)	5.90%
Forward Contract, $200 Million, Entered On May 13th, 2019 | Forward contract
Class of Stock [Line Items]
Strike price (in usd per share)	$ 12.00		$ 20.51