Business Combinations - Schedules of Assets and Liabilities Assumed (Details) - USD ($) $ in Thousands	May 01, 2018	Dec. 15, 2017	May 24, 2017	Jun. 30, 2018	Dec. 31, 2017
Liabilities assumed:
Goodwill				$ 183,162	$ 179,889
Domenick
Consideration paid:
Cash paid at closing	$ 750
Contingent payment liability (present value)	706
Value of consideration	1,456
Assets acquired:
Cash and due from banks	370
Premises and equipment	1
Other assets	316
Total assets	1,466
Liabilities assumed:
Accounts payable	657
Other liabilities	30
Total liabilities	687
Net assets acquired	779
Goodwill	677
Domenick | Customer Relationships
Assets acquired:
Intangible assets	$ 779
RBPI
Consideration paid:
Common shares issued (3,101,316)		$ 136,768
Cash in lieu of fractional shares		7
Cash-out of certain options		112
Fair value of warrants assumed		1,853
Value of consideration		$ 138,740
Shares issued (in shares)		3,101,316
Assets acquired:
Cash and due from banks		$ 17,092
Investment securities available for sale		121,587
Loans		567,308
Premises and equipment		8,264
Deferred income taxes		34,208
Bank-owned life insurance		16,550
Other assets		13,996
Total assets		784,241
Liabilities assumed:
Deposits		593,172
FHLB and other long-term borrowings		59,568
Short-term borrowings		15,000
Junior subordinated debentures		21,416
Unfavorable lease liability		322
Other liabilities		31,381
Total liabilities		720,859
Net assets acquired		63,382
Goodwill		75,358		$ 75,358	$ 72,762
RBPI | Core Deposits
Assets acquired:
Intangible assets		4,670
RBPI | Off-Market Favorable Lease
Assets acquired:
Intangible assets		$ 566
Hirshorn
Consideration paid:
Cash paid at closing			$ 5,770
Contingent payment liability (present value)			1,690
Value of consideration			7,460
Assets acquired:
Cash and due from banks			978
Premises and equipment			1,795
Accounts receivable			192
Other assets			27
Total assets			5,900
Liabilities assumed:
Accounts payable			800
Other liabilities			2
Total liabilities			802
Net assets acquired			5,098
Goodwill			2,362
Hirshorn | Trade Names
Assets acquired:
Intangible assets			195
Hirshorn | Customer Relationships
Assets acquired:
Intangible assets			2,672
Hirshorn | Noncompete Agreements
Assets acquired:
Intangible assets			$ 41