Stockholder's Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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			21,371	15,361
Warrants exercised			238,697
Warrants exercised value			$ 3,300
Changes in components of accumulated other comprehensive income (loss)
Balance at the beginning of the period	$ (25,184)	$ (4,891)	(23,947)	$ (4,716)
Other comprehensive income (loss)	2,520	29	1,283	(146)
Balance at the end of the period	(22,664)	(4,862)	(22,664)	(4,862)
Unrealized Gain (Loss) on Investments
Changes in components of accumulated other comprehensive income (loss)
Balance at the beginning of the period	(62)	(63)	(64)	(60)
Other comprehensive income (loss)	(2)	2		(1)
Balance at the end of the period	(64)	(61)	(64)	(61)
Retirement plans
Changes in components of accumulated other comprehensive income (loss)
Balance at the beginning of the period	(25,122)	(4,828)	(23,883)	(4,656)
Other comprehensive income (loss)	2,522	27	1,283	(145)
Balance at the end of the period	$ (22,600)	$ (4,801)	$ (22,600)	$ (4,801)