Share-based Compensation - Summary of Cash-Settled SARs Activity (Detail) - Cash-Settled SARs Activity [Member]	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at January 1, 2015 | shares	2,001,451
Granted, Shares | shares	913,157
Exercised, Shares | shares	(492,511)
Expired or forfeited, Shares | shares	(287,976)
Shares, Outstanding at December 31, 2015 | shares	2,134,121
Vested or expected to vest as of year end, Shares | shares	1,876,079
Exercisable at end of year, Shares | shares	463,176
Weighted-Average Exercise Price, Outstanding at January 1, 2015 | $ / shares	$ 32.76
Granted, Weighted-Average Exercise Price | $ / shares	47.48
Exercised, Weighted-Average Exercise Price | $ / shares	29.47
Expired or forfeited, Weighted-Average Exercise Price | $ / shares	37.11
Weighted-Average Exercise Price, Outstanding at December 31, 2015 | $ / shares	39.22
Vested or expected to vest as of year end, Weighted-Average Exercise Price | $ / shares	37.79
Exercisable at end of year, Weighted-Average Exercise Price | $ / shares	$ 30.38