Computation of Earnings Per Common Share and Common Share Equivalent - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic earnings per common share & common share equivalents outstanding:
Net income (loss) attributable to common shareholders	$ 152,648	$ 152,843
Weighted average common shares outstanding - basic (in thousands of shares)	256,922	265,690
Basic earnings per common share & common share equivalents outstanding	$ 0.59	$ 0.58
Diluted earnings per common share & common share equivalents outstanding:
Weighted average common shares outstanding - basic (in thousands of shares)	256,922	265,690
Impact of share-based compensation	4,254	4,077
Weighted average common shares outstanding - diluted (in thousands of shares)	261,176	269,767
Diluted earnings per common share & common share equivalents outstanding	$ 0.58	$ 0.57
Dividends per ordinary share	$ 0.22	$ 0.22