Unaudited: Quarterly Results of Operations, Common Stock Price and Dividends (Details) $ / shares in Units, $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($) shareholder $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) shareholder $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Dec. 31, 2015 USD ($) shareholder $ / shares	Dec. 31, 2014 USD ($) shareholder $ / shares	Dec. 31, 2013 USD ($)
Net sales | $	$ 95,770	$ 99,388	$ 98,896	$ 83,644	$ 89,339	$ 96,271	$ 95,662	$ 83,496		$ 377,698	$ 364,768	$ 334,122
Gross margin | $	34,457	36,101	35,143	30,075	30,895	36,465	34,831	28,951		135,776	131,142	116,989
Net earnings | $	$ 5,483	$ 8,327	$ 7,901	$ 4,227	$ 6,001	$ 10,231	$ 8,814	$ 4,632		25,938	$ 29,678	24,617
Earnings Per Share, Basic (in dollars per share) | $ / shares	$ 0.38	$ 0.58	$ 0.55	$ 0.29	$ 0.42	$ 0.71	$ 0.62	$ 0.33
Earnings Per Share, Diluted (in dollars per share) | $ / shares	0.38	0.58	0.55	0.29	0.42	0.71	0.61	0.32
Dividends declared (in dollars per share) | $ / shares	$ 0.20	0.20	0.19	0.19	0.19	0.19	0.18	0.18
Stock price (in dollars per share) | $ / shares					$ 59.35	50.45	52.65	55.10			$ 59.35
Net cash provided by operations | $									$ 24,800	35,831	$ 35,735	34,818
Net cash used for investing activities | $									$ (13,300)	$ (21,673)	$ (33,161)	$ (29,712)
Number of shareholders | shareholder	948				948					948	948
Common Stock
Stock price (in dollars per share) | $ / shares	$ 58.59	58.06	63.49	59.94					$ 58.06	$ 58.59
Common Stock | High
Stock price (in dollars per share) | $ / shares	62.00	64.41	65.87	61.35	$ 60.91	54.33	56.96	56.03	64.41	62.00	$ 60.91
Common Stock | Low
Stock price (in dollars per share) | $ / shares	$ 55.28	$ 51.63	$ 58.67	$ 54.72	$ 47.46	$ 47.32	$ 46.47	$ 47.90	$ 51.63	$ 55.28	$ 47.46
United Utilities, Inc. | Scenario, Adjustment
Net cash provided by operations | $									$ (2,900)
Net cash used for investing activities | $									$ (2,900)