Debt (Summary Of Additional Information Of Credit facilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	$ 296.6	$ 282.9
Average outstanding balance	108.3	77.2
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	201.0	201.0
Average outstanding balance	106.7	78.0
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	0.0	100.0
Average outstanding balance	0.0	1.1
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	75.0	35.0
Average outstanding balance	19.1	0.9
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	50.0	0.0
Average outstanding balance	18.0	0.0
Warehouse Facility VII [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	125.0	101.5
Average outstanding balance	61.9	7.1
Warehouse Facility VIII [Member]
Debt Instrument [Line Items]
Maximum outstanding balance	149.0	145.3
Average outstanding balance	$ 28.2	$ 7.2