COMMON SHARES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended
	Jun. 04, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Equity [Abstract]
Equity offering (in shares)	17,940,000
Common shares issued directly by the Company (in shares)	5,980,000
Common shares issuable pursuant to forward sale agreement (in shares)	11,960,000
Net proceeds from common shares issued directly by the Company	$ 426,900	$ 426,902	$ 0
Forward sale price (in dollars per share)	$ 71.48
Amount that would have been required to be paid if net settled		$ 50,200
Shares that would have been required to be delivered if net settled (in shares)		662,694
Treasury stock (in shares)		16,283,963		16,992,594
Common stock outstanding (in shares)		323,574,439		316,885,808