Equity (Details 2) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Jul. 31, 2020
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	280,000,000	280,000,000		280,000,000
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000		50,000,000
Common stock issued in connection with stock options exercised (in shares)		2,126
Common stock issued through the dividend reinvestment plan (in shares)		2,223	1,967
Number of shares of stock grants withheld (in shares)		75,542	73,103
Common stock issued through Employee Stock Purchase Plan (in shares)		12,145
Stock issued during period, shares, share-based compensation, forfeited (in shares)		3,077
Treasury Stock, Shares, Acquired		0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 316,148,000	$ 316,148,000
Issuance of common stock, net		$ 7,011,000	$ 1,599,000
Amended 2005 Stock Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 500,000,000
2020 Stock Repurchase Program
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 500,000,000
Continuous Equity Program CEP V
Class of Stock [Line Items]
Common stock sold under CEP V (in shares)	21,000	21,000
Maximum value of shares of common stock that can be sold (in dollars)	$ 1,000,000,000	$ 1,000,000,000
Shares Issued, Weighted Average Price Per Share	$ 227.60	$ 227.60
Issuance of common stock, net	$ 4,708,000	$ 4,708,000
Common stock value, remaining to be authorized under continuous equity program	$ 748,099,000	$ 748,099,000
Maximum | Continuous Equity Program CEP V
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)		153,379	165,426