Summary of Significant Accounting Policies (Computation of Dividends Paid Deduction) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash dividends paid	$ 394,487	$ 355,287	$ 318,702
cash dividends declared and paid in subsequent year that apply to current year	26,886	22,960	6,521
Cash Dividends Declared and Paid in Current Year That Apply to Previous Year	(22,960)	(6,521)	(9,286)
Dividends Paid Deduction	398,413	371,726	315,937
Less: Capital gain distributions	(33,652)	(62,165)	(62,513)
Total dividends paid deduction attributable to adjusted taxable income	$ 364,761	$ 309,561	$ 253,424