Summary of Significant Accounting Policies - Reconciliation of Earnings Attributable to Common Shares Outstanding for the Basic and Diluted EPS (Parenthetical) (Detail) (Maximum [Member]) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Maximum [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Weighted-average stock options	1,000