Subsequent Event - Additional Information (Detail) (USD $)				1 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Senior Convertible Notes Due 2018	Oct. 14, 2013 Subsequent Event	Oct. 18, 2013 Subsequent Event Senior Notes Due 2019	Oct. 14, 2013 Subsequent Event Senior Notes Due 2019	Oct. 14, 2013 Subsequent Event Senior Convertible Notes Due 2018	Oct. 14, 2013 Subsequent Event Maximum
Subsequent Event [Line Items]
Debt Instrument cash paid to holders					$ 8,000,000
Notes, principal amount outstanding including accrued and unpaid interest	293,382,000	293,382,000	122,400,000			145,400,000	122,400,000
Consideration for acquisition of assets and liabilities				55,000,000
Break-up fees				1,650,000
Reimbursement expenses								$ 750,000