Note Loans (Changes in the carrying amount and the accretable yield for the acquired loans) (Parenthetical) (Detail) - ASC Subtopic 310-30 - USD ($) $ in Thousands	Jun. 30, 2018		Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017		Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 2,033,457	[1]	$ 2,085,191	$ 2,108,993	$ 2,168,664	[1]	$ 2,245,624	$ 2,301,024
Accretable yield	1,178,042	[2]	$ 1,204,726	$ 1,214,488	1,245,672	[2]	$ 1,290,984	$ 1,288,983
Non-credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	1,500,000				1,600,000
Accretable yield	$ 900,000				$ 900,000

[1] At June 30, 2018, includes $1.5 billion of loans considered non-credit impaired at the acquisition date (June 30, 2017 - $1.6 billion).

[2] At June 30, 2018, includes $0.9 billion of loans considered non-credit impaired at the acquisition date (June 30, 2017 - $0.9 billion).