Dividend Availability and Regulatory Matters Dividend Availability and Regulatory Matters (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Dividends Paid Exceeded Earnings	$ (28,500,000)
Proceeds from Dividends Received	684,000,000
Retained earnings	$ 1,182,674,000	$ 723,471,000
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	6.00%
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital Required to be Well Capitalized	6.50%	6.50%
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Deferred Tax Assets, Regulatory Assets and Liabilities	$ 489,000
Common Equity Tier One Capital Ratio	4.50%
Supplementary Leverage Ratio	4.00%
Subordinated debentures	$ 453,846,000	$ 462,437,000
Tier One Capital, Trust Preferred Securities Capital Portion	0
Tier Two Capital, Trust Preferred Securities Capital Portion	440,200,000
Pacific Western Bank [Member]
Compliance with Regulatory Capital Requirements for Mortgage Companies [Line Items]
Retained earnings	643,900,000
Deferred Tax Assets, Regulatory Assets and Liabilities	$ 39,000