Earnings Per Share ("EPS"): (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator
Income from continuing operations									$ 522,912	$ 1,606,931	$ 159,023
Income from discontinued operations									0	0	289,936
Net income attributable to noncontrolling interests									(35,350)	(107,889)	(28,869)
Net income attributable to the Company	$ 414,959	$ 33,597	$ 14,395	$ 24,611	$ 1,429,221	$ 35,914	$ 16,088	$ 17,819	487,562	1,499,042	420,090
Allocation of earnings to participating securities									1,493	1,576	397
Numerator for basic and diluted earnings per share—net income attributable to common stockholders - basic									486,069	1,497,466	419,693
Numerator for basic and diluted earnings per share—net income attributable to common stockholders - diluted									$ 486,069	$ 1,497,466	$ 419,693
Denominator (in shares)
Denominator for basic earnings per share—weighted average number of common shares outstanding									157,916	143,144	139,598
Effect of dilutive securities (in shares)
Share and unit based compensation									144	147	82
Denominator for diluted earnings per share—weighted average number of common shares outstanding									158,060	143,291	139,680
Earnings per common share—basic: (in dollars per share)
Income from continuing operations (dollars per share)									$ 3.08	$ 10.46	$ 1.07
Discontinued operations (dollars per share)									0.00	0.00	1.94
Net income attributable to common stockholders (dollars per share)	$ 2.65	$ 0.21	$ 0.09	$ 0.15	$ 9.52	$ 0.25	$ 0.11	$ 0.13	3.08	10.46	3.01
Earnings per common share—diluted: (in dollars per share)
Income from continuing operations (dollars per share)									3.08	10.45	1.06
Discontinued operations (dollars per share)									0.00	0.00	1.94
Net income attributable to common stockholders (dollars per share)	$ 2.65	$ 0.21	$ 0.09	$ 0.15	$ 9.51	$ 0.25	$ 0.11	$ 0.13	$ 3.08	$ 10.45	$ 3.00