Loans - Changes in the carrying amount and the accretable yield for the acquired loans - Parenthetical (Details) - ASC Subtopic 310-30 - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable
Carrying amount	$ 1,702,374	$ 1,789,237	$ 1,883,556	$ 1,990,622	$ 2,033,457	$ 2,108,993
Accretable yield	1,019,659	$ 1,042,407	$ 1,092,504	1,122,732	$ 1,178,042	$ 1,214,488
Non-credit Impaired Loans
Accounts, Notes, Loans and Financing Receivable
Carrying amount	1,200,000			1,500,000
Accretable yield	$ 700,000			$ 800,000