Stockholder's Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2010
Stockholders' Equity
Warrants issued (in shares)					1,481,055
Exercise Price (in dollars per share)					$ 14.00
Shares of common stock issued on exercise of warrants			137,636	15,361
Warrants exercised			238,697
Warrants exercised value			$ 3,300
Warrants outstanding (in shares)	504,621		504,621
Changes in components of accumulated other comprehensive income (loss)
Balance at the beginning of the period	$ (22,664)	$ (4,862)	$ (23,947)	$ (4,716)
Other comprehensive income (loss)	(5,430)	23	(4,147)	(123)
Balance at the end of the period	(28,094)	(4,839)	(28,094)	(4,839)
Unrealized Gain (Loss) on Investments
Changes in components of accumulated other comprehensive income (loss)
Balance at the beginning of the period	(64)	(61)	(64)	(60)
Other comprehensive income (loss)	(1)	(3)	(1)	(4)
Balance at the end of the period	(65)	(64)	(65)	(64)
Retirement plans
Changes in components of accumulated other comprehensive income (loss)
Balance at the beginning of the period	(22,600)	(4,801)	(23,883)	(4,656)
Other comprehensive income (loss)	(5,429)	26	(4,146)	(119)
Balance at the end of the period	$ (28,029)	$ (4,775)	$ (28,029)	$ (4,775)