Merger - Summary of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Aug. 01, 2019	Sep. 30, 2019	Dec. 31, 2018
Purchase price consideration:
Stock	$ 3,018,556
Fair value of assets acquired:
Cash and cash equivalents	975,014
Federal Home Loan Bank and Federal Reserve Bank stocks	218,582
Investment securities	3,774,738
Loans held-for-sale	44,532
Loans and leases	15,726,213
Premises and equipment	140,219
Loan servicing rights	59,567
Other intangible assets	201,568
Net deferred tax asset	49,345
Other assets	553,796
Total assets acquired	21,743,574
Fair value of liabilities assumed:
Deposits	16,418,019
Short-term borrowings	2,629,426
Long-term borrowings	442,323
Other liabilities	345,604
Total liabilities assumed	19,835,372
Fair value of net identifiable assets	1,908,202
Goodwill	$ 1,110,354	$ 1,265,111	$ 154,757