Business Segments - Additional Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2015 branch	Dec. 31, 2015 USD ($)
Regional Bank [Member] [Domain] | Maximum
Business segments
Customer deposits and investment balances servicing level		$ 500,000,000
Consumer and Business Banking Division [Member] [Member] | California
Business segments
Number of full-service branches | branch	329
Consumer and Business Banking Division [Member] [Member] | Washington and Oregon
Business segments
Number of full-service branches | branch	26
Commercial Banking | Maximum
Business segments
Corporate customers revenues		500,000,000
US Corporate Banking | Minimum
Business segments
Corporate customers revenues		500,000,000
Retail Banking Division | Regional Bank [Member] [Domain] | Maximum
Business segments
Customer deposits and investment balances servicing level		3,000,000
Wealth Markets Division | Regional Bank [Member] [Domain] | Minimum
Business segments
Customer deposits and investment balances servicing level		$ 3,000,000