Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Value of share equivalents
Market price of Company's stock	$ 81.50	$ 59.73
Phantom Stock and Performance Stock Units
Number of share equivalents
Balance at beginning of the period (in shares)	472,830,000	462,430,000
Granted (in shares)	105,048,000	192,359,000
Forfeited share equivalents (in shares)	(15,104,000)	(16,283,000)
Vested share equivalents (in shares)	(150,409,000)	(147,511,000)
Balance at end of the period (in shares)	412,365,000	490,995,000
Value of share equivalents
Balance at beginning of the period (in shares)	$ 39,600	$ 25,466
Granted (in shares)	8,561	11,490
Forfeited share equivalents (in shares)	(1,231)	(973)
Vested share equivalents (in shares)	(14,246)	(7,452)
Balance at end of the period (in shares)	$ 33,608	$ 29,327