Accumulated Other Comprehensive Income/(Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated unrealized gain (loss) on Available-For-Sale Securities, Net of Tax
Beginning balance	$ (27,962)	$ 5,592
Other comprehensive income /(loss)	37,607	(33,554)	5,725
Ending balance	9,645	(27,962)	5,592
Accumulated Other Comprehensive Income/(Loss)
Beginning balance	(27,962)	5,592
Other comprehensive income/(loss)	37,607	(33,554)	5,725
Ending balance	$ 9,645	$ (27,962)	$ 5,592