Stock-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock-based compensation
Maximum number of awards that may be received by an individual in any one calendar year (in shares)	100,000
Number of shares of common stock remaining available for future grants of stock options, restricted stock or other forms of stock-based compensation under the 2001 Plan	87,202
Stock-based compensation expense	$ 934	$ 1,082	$ 848
Cost of revenues
Stock-based compensation
Stock-based compensation expense	174	188	158
Selling, general and administrative expense
Stock-based compensation
Stock-based compensation expense	760	894	690
Maximum
Stock-based compensation
Number of shares of common stock that may be subject to outstanding awards granted under the 2001 Plan	650,000
Stock options
Stock-based compensation
Expiration period	10 years
Stock Options
Outstanding at the beginning of the period (in shares)	55,400
Granted (in shares)	9,900
Exercised (in shares)	(10,500)
Outstanding at the end of the period (in shares)	54,800	55,400
Exercisable at the end of the period (in shares)	54,800
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 38.13
Granted (in dollars per share)	$ 57.74
Exercised (in dollars per share)	$ 33.41
Outstanding at the end of the period (in dollars per share)	$ 42.58	$ 38.13
Exercisable at the end of the period (in dollars per share)	$ 42.58
Aggregate Intrinsic Value
Outstanding at the beginning of the period	603
Granted	34
Exercised	(263)	(559)	(606)
Outstanding at the end of the period	1,019	603
Exercisable at the end of the period	1,019
Additional disclosures
Weighted-average fair value of stock options granted during the year (in dollars per share)	$ 12.47	$ 9.51	$ 13.99
Weighted-average remaining contractual life for stock options	6 years 14 days	6 years 2 months 16 days	5 years 7 months 20 days
Total fair value of stock options vested during the year	123	94	133
Total intrinsic value of stock options exercised during the year	263	559	606
Weighted-average remaining contractual life of the outstanding and exercisable stock options	6 years 14 days
Non-vested stock options	0
Weighted-average assumptions used to estimate the fair value for the stock options
Dividend yield (as a percent)	0.00%
Expected life	3 years
Stock options | Minimum
Stock-based compensation
Vesting period	0 years
Weighted-average assumptions used to estimate the fair value for the stock options
Risk-free interest rates (as a percent)	0.34%	0.36%	0.39%
Volatility factor (as a percent)	0.304%	0.278%	0.351%
Stock options | Maximum
Stock-based compensation
Vesting period	3 years
Weighted-average assumptions used to estimate the fair value for the stock options
Risk-free interest rates (as a percent)	0.77%	0.51%	1.21%
Volatility factor (as a percent)	0.307%	0.288%	0.411%
Stock options | Weighted-average
Weighted-average assumptions used to estimate the fair value for the stock options
Risk-free interest rates (as a percent)	0.65%	0.40%	0.56%
Volatility factor (as a percent)	0.306%	0.286%	0.364%
Restricted stock
Restricted Stock
Non-vested at the beginning of the period (in shares)	22,378
Granted (in shares)	16,425
Vested (in shares)	(18,315)
Forfeited (in shares)	(208)
Non-vested at the end of the period (in shares)	20,280	22,378
Weighted-Average Grant-Date Fair Value
Non-vested at the beginning of the period (in dollars per share)	$ 44.59
Granted (in dollars per share)	$ 55.55
Vested (in dollars per share)	$ 46.46
Forfeited (in dollars per share)	$ 52.54
Non-vested at the end of the period (in dollars per share)	$ 51.69	$ 44.59
Additional disclosures
Total fair value of restricted stock vested during the year	811	988	715
Total compensation cost not yet recognized	$ 853
Weighted-average period for recognition of total compensation cost not yet recognized	1 year 18 days
Restricted stock | Minimum
Stock-based compensation
Vesting period	6 months
Restricted stock | Maximum
Stock-based compensation
Vesting period	5 years