ATM common stock offering program and forward equity sales agreements (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Jan. 06, 2020	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Shares of common stock authorized		200,000,000.0	200,000,000.0	200,000,000
Proceeds from the issuance of common stock			$ 1,216,445	$ 1,293,301	$ 1,275,397
ATM Common Stock Offering Program, Established August 2018
Class of Stock [Line Items]
Issuance of common stock (in shares)			602,484
Weighted average price per share		$ 145.58	$ 145.58
Proceeds from the issuance of common stock			$ 86,100
Common Stock Value Available for Future Issuance		$ 22,500	$ 22,500
Forward Equity Sales Agreements Entered in June 2019 and Under ATM Program Established in August 2018
Class of Stock [Line Items]
Shares of common stock authorized		8,100,000	8,100,000
Weighted average price per share		$ 139.32	$ 139.32
Proceeds from the issuance of common stock			$ 1,100,000
Forward Equity Sales Agreements Entered in June 2019 and Under ATM Program Established in August 2018 | ATM Common Stock Offering Program, Established August 2018
Class of Stock [Line Items]
Issuance of common stock (in shares)			8,700,000
Proceeds from the issuance of common stock			$ 1,200,000
Forward Equity Sales Agreements Entered in June 2019
Class of Stock [Line Items]
Write off of Stock Issuance Costs		$ 700
Subsequent Event | Forward Equity Sales Agreements Entered in January 2020
Class of Stock [Line Items]
Shares of common stock authorized	6,900,000
Weighted average price per share	$ 155.00
Proceeds from the issuance of common stock	$ 1,000,000