Equity Transactions - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Share repurchases (in shares)				734,967	1,037,262
Acquisition of common stock				$ 83.1	$ 100.7
Amount remaining under total repurchase authorization		$ 403.2		$ 403.2
Preferred stock, shares issued (in shares)		2,875,000		2,875,000		2,875,000
Preferred stock dividends		$ 4.6	$ 4.6	$ 9.3	$ 9.3
MCPS
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	2,875,000
Public Offering price (in dollars per share)	$ 100.00
Net proceeds from sale of stock	$ 276.4
Share interest rate				6.50%		6.50%
Liquidation price (in dollars per share)		$ 100.00		$ 100.00
Minimum | MCPS
Class of Stock [Line Items]
Stock conversion ratio (in shares)	0.9385
Maximum | MCPS
Class of Stock [Line Items]
Stock conversion ratio (in shares)	1.1262