Stockholder's Equity - Changes in the Number of Ordinary Shares Outstanding and Treasury Shares Held by the Company (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Apr. 30, 2017
Shares Outstanding [Abstract]
Beginning balance	241,388,277	239,016,924
Common stock issued	43,679,124	3,304,808
Purchase of common stock	(1,040,581)	(933,455)
Ending balance	284,026,820	241,388,277
Shares Held as Treasury Shares [Abstract]
Beginning balance	8,302,004	7,824,204
Purchase of common stock	1,040,581	933,455
Retirement of common stock	(843,564)	(455,655)
Ending balance	8,499,021	8,302,004
Common stock, shares issued	292,525,841	249,690,281	40,800,000