Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent - Computation of basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Basic earnings per ordinary share and ordinary share equivalents:
Net income (loss) attributable to common shareholders									$ (560,398)		$ 440,968	$ 1,207,152
Weighted average ordinary shares outstanding									259,894		278,957	286,194
Basic earnings per ordinary share & ordinary share equivalents outstanding (in Dollars per share)	$ 0.11	$ (4.06)	$ 1.16	$ 0.58	$ 1.13	$ 0.26	$ 0.16	$ 0.07	$ (2.16)		$ 1.58	$ 4.22
Diluted earnings per ordinary share and ordinary share equivalents:
Weighted average ordinary shares outstanding									259,894		278,957	286,194
Impact of share based compensation and certain conversion features									0		3,801	4,805
Weighted average ordinary shares outstanding - diluted									259,894		282,758	290,999
Diluted earnings per ordinary share & ordinary share equivalents outstanding (in Dollars per share)	$ 0.11	$ (4.06)	$ 1.14	$ 0.57	$ 1.12	$ 0.25	$ 0.15	$ 0.07	$ (2.16)	[1]	$ 1.56	$ 4.15
Dividends per share paid on ordinary shares									$ 0.88		$ 0.80	$ 0.72

[1] Due to the net loss in the period, basic and diluted earnings per common share are calculated using the basic weighted average common shares outstanding for the year ended December 31, 2017. The shares excluded from the calculation amounted to approximately 3.7 million.