Equity Financing - Additional Information (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	0 Months Ended	1 Months Ended		2 Months Ended	12 Months Ended
	Jul. 03, 2013	Jan. 31, 2013	Apr. 30, 2011	Oct. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Common stock issued		87	3,800	2,000	3,400	4,900
Common stock average price per share			$ 9.00			$ 25.25
Net proceeds from issue of common stock		$ 2.1	$ 32.1	$ 36.2	$ 123.0	$ 118.1
Common stock shares to be sold at market price	$ 125