Stock-Based Compensation Plans - PSUA Activities (Detail) - Performance Shares - $ / shares		9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015
Summary of Performance Share Unit Awards outstanding, Number of Units
Outstanding, Beginning Balance		262,124
Granted	[1]	413,959
Vested		(175,306)
Forfeited		(42,603)
Outstanding, Ending Balance		458,174
Summary of Performance Share Unit Awards outstanding, Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance, weighted average grant date fair value		$ 64.77
Granted, weighted average grant date fair value		36.64	[1]	$ 56.78
Vested, weighted average grant date fair value		53.01
Forfeited, weighted average grant date fair value		46.09
Outstanding, Ending Balance, weighted average grant date fair value		$ 45.60

[1] Amounts granted reflect the number of performance units granted; however, the actual payout of shares will be between zero percent and 150% of the performance units granted depending on the total shareholder return ranking compared to the peer companies at the end of the three-year performance period.