Summary of Estimated Future Compensation Cost Related to Share-based Awards Granted to Employees Under Long-term Incentive Plans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Compensation Expense	$ 20,186
Expected Weighted-average Recognition (Years)	2 years 6 months
Stock Option And Stock Appreciation Rights
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Compensation Expense	2,698	[1]
Expected Weighted-average Recognition (Years)	1 year 6 months	[1]
Performance Share
Unrecognized Share Based Compensation Expense [Line Items]
Unrecognized Compensation Expense	$ 17,488
Expected Weighted-average Recognition (Years)	2 years 8 months 12 days

[1] Stock-Only Stock Appreciation Rights (SOSARs)