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Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent
Federal statutory income tax rate			21.00%	35.00%
California franchise tax, net of federal tax benefit			8.00%	6.90%
Write down of federal deferred tax assets, net			0.00%	10.50%
Tax exempt interest on municipal securities and loans			(2.40%)	(6.10%)
Tax exempt earnings on bank owned life insurance			(0.40%)	(1.00%)
Non-deductible acquisition related expenses			0.00%	0.80%
Low income housing and qualified zone academy bond tax credits			(0.50%)	(0.40%)
Stock-based compensation excess tax benefit			(0.60%)	(0.30%)
Other			(0.20%)	(0.80%)
Effective Tax Rate			24.90%	44.60%
Write-down to net deferred tax assets recorded as income tax expense	$ 3.0	$ 3.0

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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