Share-Based Compensation - Schedule of Share and Dividend Equivalent Share Award Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Value of share equivalents
Market price of Company's stock	$ 82.15	$ 67.12
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)	111,119,000	200,761,000
Forfeited share equivalents (in shares)	(22,956,000)	(27,267,000)
Vested share equivalents (in shares)	(158,573,000)	(158,491,000)
Balance at end of the period (in shares)	402,420,000	477,433,000
Value of share equivalents
Balance at beginning of the period (in shares)	$ 39,600	$ 25,466
Granted (in shares)	9,128	13,475
Forfeited share equivalents (in shares)	(1,886)	(1,830)
Vested share equivalents (in shares)	(14,903)	(8,161)
Balance at end of the period (in shares)	$ 33,059	$ 32,045