Acquisition Proforma Net Income (Details) - Blue Hills Bancorp, Inc. [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Interest Income (Expense), after Provision for Loan Loss	$ 105,019	$ 90,050	$ 208,327	$ 176,840
Business Acquisition, Pro Forma Net Income (Loss)	$ 30,628	$ 37,575	$ 30,062	$ 71,713