Earnings Per Share - Additional Information (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares outstanding and trading	244,965,000		244,965,000		243,239,000
Additional conditionally authorized shares without additional shareholder approval	53,000,000		53,000,000
Current nominal value per share (usd per share)	$ 0.01		$ 0.01		$ 0.01
Number of shares repurchased, shares	0		0
Equity Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares excluded from the diluted net income per share	12,100,000	10,600,000	12,100,000	1,500,000