Business Combination - Summary of Estimated Fair Values of Assets Acquired and Liabilities Assumed at Date of Acquisition (Detail) - USD ($) $ in Thousands	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Assets acquired:
Bank Owned Life Insurance		$ 222,482	$ 134,847
Liabilities assumed:
Goodwill recorded in the merger		$ 338,442	$ 150,501
Sun Bancorp, Inc.
Business Acquisition [Line Items]
Total Purchase Price:	$ 474,900
Assets acquired:
Cash and cash equivalents	68,632
Securities	254,522
Loans	1,517,345
Accrued interest receivable	5,621
Bank Owned Life Insurance	85,238
Deferred tax asset	57,574
Other assets	43,202
Core deposit intangible	11,897
Total assets acquired	2,044,031
Liabilities assumed:
Deposits	(1,616,073)
Borrowings	(127,727)
Other liabilities	(13,242)
Total liabilities assumed	(1,757,042)
Net assets acquired	286,989
Sun Bancorp, Inc. | Book Value
Assets acquired:
Cash and cash equivalents	68,632
Securities	254,522
Loans	1,541,868
Accrued interest receivable	5,621
Bank Owned Life Insurance	85,238
Deferred tax asset	55,710
Other assets	49,561
Core deposit intangible	0
Total assets acquired	2,061,152
Liabilities assumed:
Deposits	(1,614,910)
Borrowings	(142,567)
Other liabilities	(14,372)
Total liabilities assumed	(1,771,849)
Net assets acquired	289,303
Goodwill recorded in the merger	187,941
Sun Bancorp, Inc. | Purchase Accounting Adjustments
Assets acquired:
Securities	0
Loans	(24,523)
Accrued interest receivable	0
Bank Owned Life Insurance	0
Deferred tax asset	1,864
Other assets	(6,359)
Core deposit intangible	11,897
Total assets acquired	(17,121)
Liabilities assumed:
Deposits	(1,163)
Borrowings	14,840
Other liabilities	1,130
Total liabilities assumed	14,807
Net assets acquired	$ (2,314)