Employee Benefits (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Benefits
Maximum contribution by participants under the 401(k) savings plan (as a percent)	60.00%
Employer's matching contribution in common stock as a percentage of a participant's total compensation	4.50%
Common stock issued under the 401(k) savings plan (in shares)	267,329	179,336	68,558
Related expense for common stock issued under the 401(k) savings plan	$ 397	$ 408	$ 529