Restructuring Charges (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Restructuring Charges
Restructuring liability expected to be paid	$ 1,400,000
Severance
Restructuring charges
Restructuring costs accrued and unpaid		700,000
Changes in restructuring liability
Balance at the beginning of the period	659,000
Severance and related costs	1,801,000
Cash payments	(1,108,000)
Balance at the end of the period	$ 1,352,000