Purchased Credit Impaired ("PCI") Loans - Rollforward of PCI Loans, Net of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 69,743	$ 33,925
Principal reductions and interest payments	(45,668)	(24,530)
Acquisitions	0	49,155
Accretion of loan discount	6,654	7,573
Changes in contractual and expected cash flows due to remeasurement	14,491	9,957
Reductions due to disposals	0	(6,337)
Balance at end of period	45,220	69,743
Contractual Cashflows
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	112,711	66,003
Principal reductions and interest payments	(45,668)	(24,530)
Acquisitions	0	68,763
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	6,114	13,978
Reductions due to disposals	0	(11,503)
Balance at end of period	73,157	112,711
Non-accretable Difference
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	29,006	18,902
Principal reductions and interest payments	0	0
Acquisitions	0	14,296
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	13,707	1,465
Reductions due to disposals	0	(2,727)
Balance at end of period	15,299	29,006
Accretable Yield
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	13,962	13,176
Principal reductions and interest payments	0	0
Acquisitions	0	5,312
Accretion of loan discount	6,654	7,573
Changes in contractual and expected cash flows due to remeasurement	5,330	5,486
Reductions due to disposals	0	(2,439)
Balance at end of period	$ 12,638	$ 13,962