Goodwill and Other Intangible Assets (Core Deposit Intangibles) (Details) - Core Deposit Intangibles - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross balance	$ 86,099,000		$ 100,166,000
Accumulated amortization	67,562,000		79,112,000
Net carrying balance	18,537,000		$ 21,054,000
Write-off upon dispositions	0	$ 0
Desert Community Bank
Finite-Lived Intangible Assets [Line Items]
Write-off upon dispositions	$ 1,000,000