COMMON SHARES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended			4 Months Ended	7 Months Ended	12 Months Ended
	Jun. 15, 2020	Mar. 26, 2020	Mar. 23, 2020	Dec. 30, 2019	Dec. 31, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 15, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Equity offering (in shares)	6,000,000						5,980,000
Price per share (in dollars per share)	$ 86.26							$ 86.26
Net proceeds from common shares issued directly by the Company	$ 509,200	$ 314,100	$ 105,700					$ 929,000	$ 852,300	$ 928,992	$ 852,254	$ 0
Common shares issuable pursuant to forward sale agreement (in shares)	11,960,000	4,460,000	1,500,000		6,000,000
Forward sale price (in dollars per share)				$ 71.48
Common shares issued directly by the Company (in shares)						5,960,000
Treasury stock (in shares)					14,864,379				15,977,757	14,864,379	15,977,757
Common stock outstanding (in shares)					342,954,023				329,880,645	342,954,023	329,880,645