Share-Based Compensation - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended
	May 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration date		May 10, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	8,815,000			6,550,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	2,265,000
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Number of Shares Per Employee		2,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		3,490,545
Share-Based Compensation Arrangement By Share-Based Payment Award, Options, Grants In Period, Grant Date Fair Value		$ 700,000	$ 15,800,000	$ 7,100,000
Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)		$ 10.05	$ 15.05	$ 8.87
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options		5,500,000	2,900,000	1,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value		5,700,000	4,300,000	2,300,000
Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Grants In Period Grant Date Fair Value		24,000,000	1,300,000	2,300,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		900,000	11,100,000	9,800,000
Granted (in shares)		738,164	36,576	110,783
Weighted average grant date fair value (in dollars per share)		$ 32.46	$ 35.79	$ 20.72
Share-based Compensation		14,533,000	13,011,000	14,206,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		5,500,000	4,900,000	5,400,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options		5,300,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options		15,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost		3,000,000
Share-Based Compensation Arrangement By Share-Based Payment Award, Plan Modification, Net Effect To Share-Based Compensation Expense		$ 1,200,000	$ 1,100,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		2 years
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition		1 year 1 month 2 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition		1 year 7 months 7 days
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Performance Percentage		0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
Performance Percentage		200.00%