COMMON SHARES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended
	Jun. 04, 2019	Sep. 30, 2019	Sep. 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		$ 169,700
Shares that would have been required to be delivered if net settled (in shares)		1,985,105
Treasury stock (in shares)		16,124,979		16,992,594
Common stock outstanding (in shares)		323,733,423		316,885,808