Income Taxes - Unrecognized Tax Benefits (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, begining balance	$ 1,126		$ 891	$ 668
Additions based on tax positions related to the current year	97		236	142
Additions for tax positions of prior years	1		0	0
Additions related to Modality acquisition				83
Reductions for tax positions of prior years	(1)		(1)	(2)
Settlements	0		0	0
Unrecognized tax benefits, ending balance	$ 1,223	[1]	$ 1,126	$ 891

[1] Represents uncertain tax positions for which we could not make a reasonable estimate of the amount or the exact period of related future payments. Refer to Note 9. Income Taxes.