Stockholders' Equity, Non-controlling Interests and Loss Per Share - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended					12 Months Ended
	Feb. 13, 2012	Aug. 31, 2012	Apr. 30, 2012	Mar. 31, 2012	Feb. 29, 2012	Jan. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 30, 2012	Jun. 30, 2012
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	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
Issuance of common stock, net of fees	$ 15,200,000						$ 17,400,000	$ 0	$ 0
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							127,500,000	125,400,000
Aggregate offering price							1,300,000	700,000
Number of shares purchased				6,155
Cash paid for shares purchased by Rock from CIE				30,400,000
Additional number of shares purchased by Rock from CIE											382
Promissory note issued										19,200,000	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			3,140
Citigroup Global Markets Inc [Member]
Class of Stock [Line Items]
Number of shares sold							15,000
Aggregate offering price							$ 216,000