EARNINGS PER SHARE - Components of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net Income Attributable to Common Shareholders	$ 229,200	$ 265,300	$ 203,600	$ 244,200	$ 181,800	$ 235,900	$ 207,500	$ 253,300	$ 942,302	$ 878,485	$ 819,546
Weighted Average Common Shares Outstanding:
Basic (in shares)									317,650,180	317,336,881	316,136,748
Dilutive Effect (in shares)									804,059	1,095,806	1,280,666
Diluted (in shares)									318,454,239	318,432,687	317,417,414
Basic EPS (in dollars per share)	$ 0.72	$ 0.83	$ 0.64	$ 0.77	$ 0.57	$ 0.74	$ 0.65	$ 0.80	$ 2.97	$ 2.77	$ 2.59
Diluted EPS (in dollars per share)	$ 0.72	$ 0.83	$ 0.64	$ 0.77	$ 0.57	$ 0.74	$ 0.65	$ 0.80	$ 2.96	$ 2.76	$ 2.58