Business Combination (Details)		3 Months Ended
	May 30, 2017	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Assets		$ 9,061,234,000	$ 9,063,895,000
Deposits		7,300,179,000	$ 7,376,110,000
Estimate of total assets		$ 12,000,000,000
Bank of the Cascades [Member]
Business Acquisition [Line Items]
Number of banking offices		46
Assets		$ 3,136,672,000
Deposits		2,714,781,000
Loans Receivable, Net		2,088,174,000
Bank of the Cascades [Member]
Business Acquisition [Line Items]
Business Acquisition Conversion Rate		1.91
Estimate of Consideration Transferred		$ 595,128,000
Bank of the Cascades [Member] | Class A Common Stock
Business Acquisition [Line Items]
Business Acquisition Conversion Share Rate | $ / shares		$ 0.14864
Subsequent Event [Member] | Bank of the Cascades [Member] | Class A Common Stock
Business Acquisition [Line Items]
Business Acquisition, Expected Effective Date of Acquisition	May 30, 2017