Basis of Presentation and Consolidation (Details) (USD $)	0 Months Ended	9 Months Ended	12 Months Ended
	Jan. 14, 2014	Sep. 30, 2014	Dec. 31, 2013
Summary Of Significant Accounting Policies
Amount of stock subscriptions received			$ 43,398,000
Conversion costs			888,000
Number of shares of common stock offering on a priority basis to qualifying depositors and to the general public, including those issued to tax qualified employee benefit plans	4,827,125
Share price (in dollars per share)	$ 10.00
Net proceeds from common stock offering on a priority basis to qualifying depositors and to the general public, including those issued to tax qualified employee benefit plans	46,300,000
Amount of cash contribution to Coastway Cares Charitable Foundation II	300,000
Number of common stock shares contribution to Coastway Cares Charitable Foundation II	122,054
Total contribution to Coastway Cares Charitable Foundation II as a percentage of gross proceeds of offering	3.15%
Gross proceeds of the offering	1,500,000	1,521,000
Total number of shares of common stock outstanding upon completion of the Conversion	4,949,179
Liquidation amount	$ 27,500,000
Bancorp
Summary Of Significant Accounting Policies
Ownership percentage		100.00%
Coastway Bancorp, MHC
Summary Of Significant Accounting Policies
Ownership percentage		100.00%