Stockholders' Equity (Narrative) (Details) - USD ($)		3 Months Ended				6 Months Ended
	Apr. 26, 2022	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Oct. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)		10,000,000				10,000,000		10,000,000
Stockholders' equity		$ 11,069,700,000	$ 11,409,800,000	$ 11,823,000,000	$ 11,457,900,000	$ 11,069,700,000	$ 11,823,000,000	$ 12,016,800,000		$ 11,688,300,000
Common stock dividends (in usd per share)		$ 0.70	$ 0.70	$ 0.70	$ 0.70
Stock repurchase program, number of shares authorized to be repurchased (in shares)									25,000,000
Stock repurchase, shares (in shares)		2,844		252,304		298,254	1,651,977
Stock repurchase, aggregate cost		$ 300,000	$ 33,800,000	$ 30,200,000	$ 135,600,000	$ 34,100,000	$ 165,800,000
Average price paid per share for common stock repurchased (in usd per share)		$ 110.36		$ 119.59		$ 114.54	$ 100.38
Treasury stock, share-based compensation shares, acquired (in shares)				1,480			367,177
Preferred Stock
Class of Stock [Line Items]
Stockholders' equity		$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000		$ 884,900,000
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)		5,000				5,000		5,000
Preferred stock, without par value (in dollars per share)		$ 0				$ 0
Preferred stock, liquidation preference		$ 100,000				$ 100,000
Depository shares, liquidation preference per share (in dollars per share)		$ 1,000				$ 1,000
Preferred stock, annual dividend rate						4.60%
Preferred stock, dividend payment rate, variable rate						3.202%
Series D Preferred Stock | Preferred Stock
Class of Stock [Line Items]
Stockholders' equity		$ 493,500,000				$ 493,500,000		$ 493,500,000
Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)		16,000				16,000		16,000
Percentage of ownership interest per each depository shares		0.10%				0.10%
Preferred stock, without par value (in dollars per share)		$ 0				$ 0
Preferred stock, liquidation preference		$ 25,000				$ 25,000
Depository shares, liquidation preference per share (in dollars per share)		$ 25				$ 25
Preferred stock, annual dividend rate						4.70%
Common stock dividends (in usd per share)	$ 293.75
Series E Preferred Stock | Preferred Stock
Class of Stock [Line Items]
Stockholders' equity		$ 391,400,000				$ 391,400,000		$ 391,400,000
Series D Preferred Stock, Depositary Shares
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)		500,000				500,000
Preferred stock, shares issued (in shares)		500,000				500,000
Percentage of ownership interest per each depository shares		1.00%				1.00%
Series E Preferred Stock Depositary Shares
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)		16,000,000				16,000,000
Preferred stock, shares issued (in shares)		16,000,000				16,000,000