Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Sep. 30, 2019	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shelf registration, shares issued (in shares)	7,000,000
Shelf registration, price per share (in dollars per share)	$ 56.50
Shelf registration, net proceeds	$ 379,410
Stock issuance costs	$ 16,090		$ 17,521	$ 3,947	$ 3,836
Net proceeds			$ 542,280	$ 345,324	$ 256,764
Total allowable shares (in shares)			375,000,000	375,000,000
Total shares issued (in shares)			171,694,209	161,503,585
Shares of common stock (in shares)			7,000,000
Net proceeds			$ 395,500
DRIP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares permitted for issuance (in shares)		10,000,000
Shares of common stock (in shares)			362,918	311,048	229,696
Net proceeds			$ 19,442	$ 13,264	$ 9,391
2018 ATM Equity Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total allowable shares (in shares)			12,000,000
Total shares issued (in shares)			9,722,185
2016 ATM Equity Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total allowable shares (in shares)			12,000,000
Total shares issued (in shares)			10,044,656
ATM Equity Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issuance costs			$ 1,431	$ 3,821	$ 3,782
Shares of common stock (in shares)			2,344,022	7,378,163	5,821,366
Average price per share (net) (in dollars per share)			$ 53.71	$ 44.48	$ 41.88
Net proceeds			$ 125,905	$ 328,196	$ 243,822