Stock-Based Compensation Plans - Valuation Assumptions for Grant Date Fair Value of Performance Awards (Detail) - Performance Shares - $ / shares	3 Months Ended
	Mar. 31, 2016		Mar. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.85%		1.05%
Expected annual volatility	51.70%		33.90%
Weighted average grant date fair value per unit	$ 30.47	[1]	$ 55.17

[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.