Shareholders' Equity (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 28, 2024	Dec. 31, 2022	Oct. 28, 2021	Aug. 06, 2020	Dec. 31, 2007
Class of Stock [Line Items]
Shares registered	400,000,000		400,000,000		3,400,000
Federal net operating loss carry-forward	$ 4.0
Class A Common Stock [Member] | November 16, 2007 Registration Statement [Member]
Class of Stock [Line Items]
Shares reclassified as authorized and unissued	1,200,000
Shares registered						4,000,000.0
Class A Common Stock [Member] | February 26,2021 Registration Statement [Member]
Class of Stock [Line Items]
Securities issued	0		0
2020 Plan [Member]
Class of Stock [Line Items]
Shares registered					3,000,000.0
2010 Plan [Member]
Class of Stock [Line Items]
Shares registered					400,000
New Plan [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Stock repurchase program, remaining authorization		$ 404.7
New Plan [Member] | Class A Common Stock [Member]
Class of Stock [Line Items]
Stock repurchase program, authorized				$ 1,000.0
Real Estate Investment Trust [Member]
Class of Stock [Line Items]
Federal net operating loss carry-forward	$ 382.3