Share-Based Compensation - Unvested Restricted Stock Award Activity (Detail) - Restricted Stock And Restricted Stock Units - shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at beginning of the period (in shares)	543,258,000	507,130,000
Granted (in shares)	163,353,000	240,699,000
Forfeited (in shares)	(9,951,000)	(9,040,000)
Earned and issued (in shares)	(185,092,000)	(172,356,000)
Balance at end of the period (in shares)	511,568,000	566,433,000