CONDENSED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Ordinary share capital [Member]	Additional paid-in capital [Member]	Retained earnings [Member]	Shareholders' equity attributable to shareholders [Member]	Non-controlling interest in joint venture [Member]
Balance at Dec. 31, 2010	$ 839,161	$ 3,646	$ 485,555	$ 304,202	$ 793,403	$ 45,758
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of Class A ordinary shares, net of forfeitures	12	12	0	0	12	0
Share-based compensation expense, net of forfeitures	2,012	0	2,012	0	2,012	0
Non-controlling interest withdrawal from joint venture, net	(10,400)	0	0	0	0	(10,400)
Income (loss) attributable to non-controlling interest in joint venture	(1,649)	0	0	0	0	(1,649)
Net income (loss)	(58,951)	0	0	(58,951)	(58,951)	0
Balance at Jun. 30, 2011	770,185	3,658	487,567	245,251	736,476	33,709
Balance at Dec. 31, 2011	845,698	3,654	488,478	310,971	803,103	42,595
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issue of Class A ordinary shares, net of forfeitures	14	14	0	0	14	0
Share-based compensation expense, net of forfeitures	1,737	0	1,737	0	1,737	0
Non-controlling interest withdrawal from joint venture, net	(34,000)	0	0	0	0	(34,000)
Income (loss) attributable to non-controlling interest in joint venture	3,183	0	0	0	0	3,183
Net income (loss)	29,064	0	0	29,064	29,064	0
Balance at Jun. 30, 2012	$ 845,696	$ 3,668	$ 490,215	$ 340,035	$ 833,918	$ 11,778