Equity Financing - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	6 Months Ended	1 Months Ended
	Jan. 31, 2013	Jun. 30, 2013	Jul. 31, 2013 Subsequent Event	Aug. 07, 2013 Subsequent Event
Class of Stock [Line Items]
Common stock issued	87,000			1,000,000
Net proceeds from issue of common stock	$ 2.1	$ 37.9	$ 125.0	$ 37.9