Stock-Based Compensation Plans - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Actual payout of shares on performance units granted	150.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Actual payout of shares on performance units granted	0.00%
Stock Appreciation Rights (SARs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years
Stock Appreciation Rights (SARs) | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration term of stock units	5 years
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years	3 years
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	3 years