Equity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock, shares authorized	280,000,000	280,000,000
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock shares issued in connection with stock options exercised	109,804
Common stock shares issued through dividend reinvestment plan	2,069	2,272	3,058
Number of shares of stock grants withheld	84,710	68,565	60,319
Common shares issued under Employee Stock Purchase Plan	13,894
Number of shares forfeited	2,361
Issuance of common stock, net	$ 409,725,000	$ 52,261,000	$ 111,093,000
Continuous Equity Programs CEP IV and CEP V [Member]
Class of Stock [Line Items]
Issuance of common stock, net of withholdings (in shares)	1,942,502
Continuous Equity Program CEP IV
Class of Stock [Line Items]
Issuance of common stock, net of withholdings (in shares)	755,054
Maximum value of shares of common stock that can be sold	$ 1,000,000,000
Shares issued, weighted average price per share (in dollars per share)	$ 198.26
Issuance of common stock, net	$ 147,450,000
Continuous Equity Program CEP V [Member]
Class of Stock [Line Items]
Issuance of common stock, net of withholdings (in shares)	239,580
Maximum value of shares of common stock that can be sold	$ 1,000,000,000
Forward Contract Indexed to Issuer's Equity, Shares	947,868
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share	$ 207.96
Forward Contract Indexed To Issuer's Equity, Approximate Net Proceeds	$ 197,122,000
Shares issued, weighted average price per share (in dollars per share)	$ 208.70
Issuance of common stock, net	$ 49,250,000
Common stock value, remaining to be authorized under continuous equity program	$ 752,878,000
Maximum [Member] | Continuous Equity Program CEP IV
Class of Stock [Line Items]
Percentage of compensation received by sales agent	2.00%
Maximum [Member] | 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]
Common stock shares issued in connection with stock grants	152,502	187,010	201,824
Non-employee directors | Deferred Compensation, Share-based Payments [Member]
Class of Stock [Line Items]
Common stock shares issued in connection with stock grants	1,838