Other Assets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Aug. 31, 2011	Feb. 28, 2010
Other Assets
Filing fee related to application				$ 1,406
Filing fees refunded		584
Filing fees receivable	424
Amount of nonrefundable fees reclassified to intangible assets			$ 398