Stockholder's Equity (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 01, 2020	Feb. 28, 2019
Preferred Stock [Line Items]
Equity shelf program issuances	$ 576,196,000	$ 611,645,000	$ 364,070,000
Equity Shelf Program
Preferred Stock [Line Items]
Aggregate amount of common stock offered to sell					$ 1,500,000,000
Remaining capacity	$ 499,341,000
Repurchase Program
Preferred Stock [Line Items]
Number of shares to be repurchased (in shares)				1,000,000,000
Number of shares not included in the computation of diluted earnings per share because such options were anti-dilutive (in shares)	201,947
Share Price (in USD per share)	$ 37.89
Series I Preferred Stock
Preferred Stock [Line Items]
Equivalent number of common stock on conversion of preferred shares (in shares)		0.8857