CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data	Common Stock [Member]	Retained Earnings [Member]	Total
Balance, shares at Dec. 31, 2011	15,682
Balance at Dec. 31, 2011	$ 141,432	$ 35,549	$ 176,981msex_TotalCommonEquity
Net Income		14,396	14,396us-gaap_NetIncomeLoss
Dividend Reinvestment & Common Stock Purchase Plan	1,587		1,587
Dividend Reinvestment & Common Stock Purchase Plan, shares	86
Restricted Stock Award, Net - Employees	448		448
Restricted Stock Award, Net - Employees, shares	21
Stock Award - Board Of Directors	105		105
Stock Award - Board Of Directors, shares	6
Cash Dividends on Common Stock		(11,679)	(11,679)us-gaap_DividendsCommonStockCash
Cash Dividends on Preferred Stock		(206)	(206)us-gaap_DividendsPreferredStockCash
Balance, shares at Dec. 31, 2012	15,795
Balance at Dec. 31, 2012	143,572	38,060	181,632msex_TotalCommonEquity
Net Income		16,633	16,633us-gaap_NetIncomeLoss
Dividend Reinvestment & Common Stock Purchase Plan	1,653		1,653
Dividend Reinvestment & Common Stock Purchase Plan, shares	82
Restricted Stock Award, Net - Employees	388		388
Restricted Stock Award, Net - Employees, shares	26
Stock Award - Board Of Directors	105		105
Stock Award - Board Of Directors, shares	5
Conversion of Convertible Preferred Stock	467		467
Conversion of Convertible Preferred Stock, shares	55
Cash Dividends on Common Stock		(11,943)	(11,943)us-gaap_DividendsCommonStockCash
Cash Dividends on Preferred Stock		(190)	(190)us-gaap_DividendsPreferredStockCash
Balance, shares at Dec. 31, 2013	15,963
Balance at Dec. 31, 2013	146,185	42,560	188,745msex_TotalCommonEquity
Net Income		18,445	18,445us-gaap_NetIncomeLoss
Dividend Reinvestment & Common Stock Purchase Plan	1,493		1,493
Dividend Reinvestment & Common Stock Purchase Plan, shares	71
Restricted Stock Award, Net - Employees	434		434
Restricted Stock Award, Net - Employees, shares	33
Stock Award - Board Of Directors	105		105
Stock Award - Board Of Directors, shares	5
Conversion of Convertible Preferred Stock	451		451
Conversion of Convertible Preferred Stock, shares	52
Cash Dividends on Common Stock		(12,231)	(12,231)us-gaap_DividendsCommonStockCash
Cash Dividends on Preferred Stock		(151)	(151)us-gaap_DividendsPreferredStockCash
Balance, shares at Dec. 31, 2014	16,124
Balance at Dec. 31, 2014	$ 148,668	$ 48,623	$ 197,291msex_TotalCommonEquity

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