Gain on Sale of Rights Gain on Sale of Rights (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Gain on Sale of Rights [Abstract]
Gain on sale of rights	$ 31,719	$ 0	$ 31,719	$ 0