Stockholders' Equity, Non-controlling Interests, and Loss Per Share - Stockholders' Equity, Non-controlling Interests, and Loss Per Share - Additional Information (Detail) (USD $)	1 Months Ended
	Aug. 31, 2012	Apr. 30, 2012	Mar. 31, 2012	Feb. 29, 2012 Ratio	Jan. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Class of Stock [Line Items]
Number of shares released under contractual transfer restrictions					24,200,000
Number of shares agreed to be contributed by participating co-investors					1,800,000
Newly issued shares of common stock				1,800,000
Number of shares issued as underwriters allotment in public offering				271,697
Issue price of underwriters allotment in public offering				$ 9.00
Common stock, stock split				1.742
Registered Shares became eligible for resale under the Shelf Registration	50.00%			50.00%
Maximum aggregate common stock offering price			$ 500,000,000
Issue and sale of shares under equity distribution agreement		10,000,000
Number of shares sold						127,400,000		125,400,000
Aggregate offering price						1,300,000		700,000
Number of shares purchased			6,155
Cash paid for shares purchased by Rock to CIE			30,400,000
Additional number of shares purchased by Rock from CIE						3,140	382
Promissory note issued							28,500,000
Additional cash paid for shares purchased by Rock to CIE						19,200,000	30,400,000
Promissory note convertible into number of shares						5,773
Stock option exercise date			Nov. 15, 2012
Citigroup Global Markets Inc [Member]
Class of Stock [Line Items]
Number of shares sold						15,000
Aggregate offering price						$ 216,000