Capital Stock (Detail) - shares	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Class Of Stock [Line Items]
Beginning balance	247,144,356	169,316,460
Restricted stock grants	66,078	490,609
Restricted stock units vested	302,383	266,541
PSU-TSR units settled	19,960	0
Shares retired	0	(739)
Treasury shares issued	4,000	28,736
Ending balance	247,536,777	247,144,356
MRD
Class Of Stock [Line Items]
MRD Merger	0	77,042,749