Loans and Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 17,026,588	[1],[2]	$ 15,671,735	[1],[2]	$ 13,900,025
Unamortized premiums	17,300		18,000
Pledged loans as collateral	6,400,000
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	4,254,682		4,061,001		3,509,175
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	2,684,500		2,702,560		2,549,401
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	4,940,931		4,315,999		3,749,270
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	4,510,846		3,991,649		3,554,428
Finance Leases Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 635,629		$ 600,526		$ 537,751

[1] At December 31, 2016, the Company had pledged $6.4 billion of eligible loans as collateral to support borrowing capacity at the FHLB of Boston and the FRB of Boston.

[2] Loans and leases include net deferred fees and net premiums and discounts of $17.3 million and $18.0 million at December 31, 2016 and December 31, 2015, respectively.