Purchased Credit Impaired ("PCI") Loans - Rollforward of PCI Loans, Net of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 45,220	$ 69,741
Acquisitions	68,183
Principal reductions and interest payments	(19,285)	(22,667)
Accretion of loan discount	4,645	3,400
Changes in contractual and expected cash flows due to remeasurement	9,155	7,928
Reductions due to disposals	5,490
Balance at end of period	102,428	58,402
Contractual Cashflows
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	73,157	112,710
Acquisitions	111,963
Principal reductions and interest payments	(19,285)	(22,667)
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	7,725	3,281
Reductions due to disposals	8,709
Balance at end of period	164,851	93,324
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	15,299	29,005
Acquisitions	13,542
Principal reductions and interest payments	0	0
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	(2,057)	(8,771)
Reductions due to disposals	3,224
Balance at end of period	23,560	20,234
Accretable Yield
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	12,638	13,964
Acquisitions	30,238
Principal reductions and interest payments	0	0
Accretion of loan discount	4,645	3,400
Changes in contractual and expected cash flows due to remeasurement	627	4,124
Reductions due to disposals	5
Balance at end of period	$ 38,863	$ 14,688