Equity (Details 2) - USD ($)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jul. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	280,000,000			280,000,000
Preferred stock, shares authorized (in shares)	50,000,000			50,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period	1,902
Common stock issued through the dividend reinvestment plan (in shares)	1,967	1,594
Number of shares of stock grants withheld (in shares)	73,103	83,602
Stock Issued During Period, Shares, Employee Stock Purchase Plans	8,685
Stock issued during period, shares, share-based compensation, forfeited (in shares)	7,421
Treasury Stock, Shares, Acquired	912,733
Treasury Stock Acquired, Average Cost Per Share	$ 150.58
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 362,560,000
Issuance of common stock, net	1,599,000	$ 207,789,000
2020 Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 500,000,000
Amended 2005 Stock Repurchase Program [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 500,000,000
Continuous Equity Program CEP V [Member]
Class of Stock [Line Items]
Maximum value of shares of common stock that can be sold (in dollars)	1,000,000,000
Common stock value, remaining to be authorized under continuous equity program	752,878,000
Issuance of common stock, net	$ 0
Maximum | Continuous Equity Program CEP V [Member]
Class of Stock [Line Items]
Percentage of compensation received by sales agent	1.50%
Restricted Stock and Restricted Stock Converted From Performance Shares
Class of Stock [Line Items]
Equity instruments granted (in shares)	165,426	150,359