Stockholders' Equity Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	12 Months Ended
	Jan. 26, 2021	Jul. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 19, 2020
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Declared			$ 1.60	$ 1.52	$ 1.36
Preferred Stock, Value, Issued			$ 35	$ 35
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right						0.001
Preferred Stock, Par or Stated Value Per Share						$ 1.00
Series C Preferred Stock [Member] | Dividend Declared [Member]
Class of Stock [Line Items]
Class of Warrant or Right, Outstanding						1
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Par or Stated Value Per Share		$ 1
Stock Issued During Period, Shares, New Issues		35,000
Preferred Stock, Value, Issued		$ 35
Preferred Stock, Dividend Rate, Percentage		7.25%
Preferred Stock, Shares Authorized		30,000,000
Subsequent Event [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.41