Restructuring - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended			24 Months Ended	36 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 71	$ 30	$ 9
Quest [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs				$ 10
2016 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 33
2015 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs				$ 23
2014 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs					$ 11