COMMON SHARES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended			4 Months Ended	6 Months Ended
	Jun. 15, 2020	Mar. 26, 2020	Mar. 23, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Equity offering (in shares)	6,000,000			5,960,000	6,000,000	5,980,000
Price per share (in dollars per share)	$ 86.26
Net proceeds from common shares issued directly by the Company	$ 509,200	$ 314,100	$ 105,700				$ 929,000	$ 929,025	$ 426,902
Common shares issuable pursuant to forward sale agreement (in shares)		4,460,000	1,500,000			11,960,000
Forward sale price (in dollars per share)		$ 71.48
Treasury stock (in shares)					15,977,757		15,190,540	15,190,540
Common stock outstanding (in shares)					329,880,645		342,627,862	342,627,862