Subsequent Event (Notes)	3 Months Ended
Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	SUBSEQUENT EVENT Effective April 1, 2019, the Company completed the acquisition of Blue Hills Bancorp, Inc., parent of The Blue Hills Bank (collectively "BHB"). The acquisition resulted in the addition of eleven branch locations in Suffolk and Norfolk counties of Massachusetts, as well as Nantucket. The transaction included the acquisition of approximately $2.1 billion in loans, $196.9 million in securities, the assumption of $1.9 billion in deposits, and $124.8 million of borrowings, each at fair value. Total consideration of $667.1 million consisted of 6,166,010 shares of the Company's common stock issued, as well as $167.4 million in cash, inclusive of cash in lieu of fractional shares.

The entire disclosure for significant events or transactions that occurred after the balance sheet date through the date the financial statements were issued or the date the financial statements were available to be issued. Examples include: the sale of a capital stock issue, purchase of a business, settlement of litigation, catastrophic loss, significant foreign exchange rate changes, loans to insiders or affiliates, and transactions not in the ordinary course of business.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 855
-URI http://asc.fasb.org/topic&trid=2122774

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