Dividend Availability and Regulatory Matters Dividend Availability and Regulatory Matters (Details) $ in Thousands	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier One Leverage Capital	$ 2,657,575	$ 2,403,721
Tier One Leverage Capital to Average Assets	0.0684	0.0855
Tier One Leverage Capital Required to be Well Capitalized	$ 1,942,017	$ 1,404,880
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	0.050	0.0500
Tier One Risk Based Common Equity	$ 2,526,575	$ 2,403,721
Tier One Risk Based Common Equity to Risk Weighted Assets	8.86%	10.53%
Tier One Risk Based Common Equity Required to be Well Capitalized	$ 1,853,073	$ 1,484,450
Tier One Risk Based Common Equity Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier One Risk Based Common Equity Required to be Well Capitalized to Risk Weighted Assets Capital Conservation Buffer	7.00%	7.00%
Tier One Risk Based Capital	$ 2,657,575	$ 2,403,721
Tier One Risk Based Capital to Risk Weighted Assets	0.0932	0.1053
Tier One Risk Based Capital Required to be Well Capitalized	$ 2,280,705	$ 1,827,015
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	0.0800	0.0800
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Capital Conservation Buffer	8.50%	8.50%
Capital	$ 3,619,190	$ 3,141,992
Capital to Risk Weighted Assets	0.1269	0.1376
Capital Required to be Well Capitalized	$ 2,850,881	$ 2,283,769
Capital Required to be Well Capitalized to Risk Weighted Assets	0.1000	0.1000
Capital Required to be Well Capitalized to Risk Weighted Assets Capital Conservation Buffer	10.50%	10.50%
Pacific Western Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier One Leverage Capital	$ 2,717,374	$ 2,673,960
Tier One Leverage Capital to Average Assets	0.0700	0.0953
Tier One Leverage Capital Required to be Well Capitalized	$ 1,940,510	$ 1,403,208
Tier One Leverage Capital Required to be Well Capitalized to Average Assets		0.0500
Tier One Risk Based Common Equity	$ 2,717,374	$ 2,673,960
Tier One Risk Based Common Equity to Risk Weighted Assets	9.56%	11.73%
Tier One Risk Based Common Equity Required to be Well Capitalized	$ 1,847,853	$ 1,481,599
Tier One Risk Based Common Equity Required to be Well Capitalized to Risk Weighted Assets		6.50%
Tier One Risk Based Common Equity Required to be Well Capitalized to Risk Weighted Assets Capital Conservation Buffer	7.00%	7.00%
Tier One Risk Based Capital	$ 2,717,374	$ 2,673,960
Tier One Risk Based Capital to Risk Weighted Assets	0.0956	0.1173
Tier One Risk Based Capital Required to be Well Capitalized	$ 2,274,281	$ 1,823,506
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets		0.0800
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Capital Conservation Buffer	8.50%	8.50%
Capital	$ 3,355,403	$ 2,959,853
Capital to Risk Weighted Assets	0.1180	0.1299
Capital Required to be Well Capitalized	$ 2,842,851	$ 2,279,383
Capital Required to be Well Capitalized to Risk Weighted Assets		0.1000
Capital Required to be Well Capitalized to Risk Weighted Assets Capital Conservation Buffer	10.50%	10.50%