CONSOLIDATED STATEMENTS OF COMMON STOCKHOLDERS' EQUITY AND COMPREHENSIVE INCOME (Parenthetical) (USD $)	12 Months Ended
Dec. 31, 2013
Statement of Stockholders' Equity [Abstract]
Conversion of Convertible Preferred Stock Value Per Share	$ 8.00

Refers to per share value of conversion of convertible preferred stock.

No definition available.

Name:	msex_ConversionOfConvertiblePreferredStockValuePerShare
Namespace Prefix:	msex_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration