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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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LOANS AND LEASES AND ALLOWANCE FOR LOAN AND LEASE LOSSES - Allowance for Loan and Lease Losses and Recorded Investment Excluding Accrued Interest in Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 40,444	$ 35,533	$ 29,480
Charge-offs	(5,581)	(2,618)	(1,942)
Recoveries	771	2,258	526
Provision	13,699	5,271
Balance at end of year	49,333	40,444	35,533
Individually evaluated for impairment				$ 1,217	$ 243
Collectively evaluated for impairment				48,116	40,097
Total ending allowance balance	40,444	35,533	29,480	49,333	40,444
Loans:
Individually evaluated for impairment				24,050	13,352
Collectively evaluated for impairment				6,635,357	5,879,574
Total ending loan balances				6,659,407	6,034,752
PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	104
Balance at end of year	0	104
Total ending allowance balance	104	104		0	104
Loans:
Total ending loan balances				0	141,826
Commercial \| Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	7,584	5,850
Charge-offs	(1,730)	(166)
Recoveries	54	225
Provision	8,372	1,675
Balance at end of year	14,280	7,584	5,850
Individually evaluated for impairment				498	0
Collectively evaluated for impairment				13,782	7,584
Total ending allowance balance	7,584	5,850	5,850	14,280	7,584
Loans:
Individually evaluated for impairment				3,582	2,429
Collectively evaluated for impairment				1,698,369	1,515,771
Total ending loan balances				1,701,951	1,522,960
Commercial \| Commercial and industrial \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	0
Balance at end of year	0	0
Total ending allowance balance	0	0		0	0
Loans:
Total ending loan balances				0	4,760
Commercial \| Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	5,467	4,252
Charge-offs	(113)	(414)
Recoveries	0	807
Provision	(383)	822
Balance at end of year	4,971	5,467	4,252
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				4,971	5,462
Total ending allowance balance	5,467	4,252	4,252	4,971	5,467
Loans:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				717,415	728,777
Total ending loan balances				717,415	729,959
Commercial \| Commercial real estate \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	5
Balance at end of year	0	5
Total ending allowance balance	5	5		0	5
Loans:
Total ending loan balances				0	1,182
Commercial \| Multifamily
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	11,376	6,012
Charge-offs	0	0
Recoveries	0	169
Provision	1,889	5,195
Balance at end of year	13,265	11,376	6,012
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				13,265	11,376
Total ending allowance balance	11,376	6,012	6,012	13,265	11,376
Loans:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				1,816,141	1,365,262
Total ending loan balances				1,816,141	1,365,262
Commercial \| Multifamily \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	0
Balance at end of year	0	0
Total ending allowance balance	0	0		0	0
Loans:
Total ending loan balances				0	0
Commercial \| SBA
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	939	683
Charge-offs	(625)	0
Recoveries	422	500
Provision	965	(244)
Balance at end of year	1,701	939	683
Individually evaluated for impairment				435	0
Collectively evaluated for impairment				1,266	920
Total ending allowance balance	939	683	683	1,701	939
Loans:
Individually evaluated for impairment				944	0
Collectively evaluated for impairment				77,755	71,168
Total ending loan balances				78,699	73,840
Commercial \| SBA \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	19
Balance at end of year	0	19
Total ending allowance balance	19	19		0	19
Loans:
Total ending loan balances				0	2,672
Commercial \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	2,015	1,530
Charge-offs	(29)	0
Recoveries	0	0
Provision	1,332	485
Balance at end of year	3,318	2,015	1,530
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				3,318	2,015
Total ending allowance balance	2,015	1,530	1,530	3,318	2,015
Loans:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				182,960	125,100
Total ending loan balances				182,960	125,100
Commercial \| Construction \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	0
Balance at end of year	0	0
Total ending allowance balance	0	0		0	0
Loans:
Total ending loan balances				0	0
Commercial \| Lease financing
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	6	2,195
Charge-offs	0	(974)
Recoveries	32	283
Provision	(38)	(1,498)
Balance at end of year	0	6	2,195
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				0	6
Total ending allowance balance	6	2,195	2,195	0	6
Loans:
Individually evaluated for impairment				0	0
Collectively evaluated for impairment				13	379
Total ending loan balances				13	379
Commercial \| Lease financing \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	0
Balance at end of year	0	0
Total ending allowance balance	0	0		0	0
Loans:
Total ending loan balances				0	0
Consumer \| Single Family Residential Mortgage
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	12,075	13,854
Charge-offs	(2,806)	(1,057)
Recoveries	1	248
Provision	1,726	(970)
Balance at end of year	10,996	12,075	13,854
Individually evaluated for impairment				277	243
Collectively evaluated for impairment				10,719	11,752
Total ending allowance balance	12,075	13,854	13,854	10,996	12,075
Loans:
Individually evaluated for impairment				14,699	10,629
Collectively evaluated for impairment				2,040,950	1,962,789
Total ending loan balances				2,055,649	2,106,630
Consumer \| Single Family Residential Mortgage \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	80
Balance at end of year	0	80
Total ending allowance balance	80	80		0	80
Loans:
Total ending loan balances				0	133,212
Consumer \| Other Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	982	1,157
Charge-offs	(278)	(7)
Recoveries	262	26
Provision	(164)	(194)
Balance at end of year	802	982	1,157
Individually evaluated for impairment				7	0
Collectively evaluated for impairment				795	982
Total ending allowance balance	982	1,157	$ 1,157	802	982
Loans:
Individually evaluated for impairment				4,825	294
Collectively evaluated for impairment				101,754	110,328
Total ending loan balances				106,579	110,622
Consumer \| Other Consumer \| PCI Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	0
Balance at end of year	0	0
Total ending allowance balance	$ 0	$ 0		0	0
Loans:
Total ending loan balances				$ 0	$ 0