Fair Value Measurements - Schedule of Fair Values of Financial Assets and Liabilities (Parenthetical) (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change of control aggregate cash payments, per share	$ 12.00
Liability for the Change of Control	$ 0.2