Subsequent Events (Details Textuals)			3 Months Ended
	May 01, 2017 $ / shares	Apr. 06, 2017 USD ($) bank_branch $ / shares shares	Mar. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares	Mar. 31, 2016 $ / shares
Subsequent Event [Line Items]
Common Stock par value (usd per share)			$ 0.01	$ 0.01
Dividends declared per share (usd per share)			$ 0.50	$ 0.50	$ 0.5
Subsequent Event [Member]
Subsequent Event [Line Items]
number of branches | bank_branch		87
Subsequent Event [Member] | Dividend Declared
Subsequent Event [Line Items]
Dividends declared per share (usd per share)	$ 0.5
California United Bancorp [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Business Combination, Consideration Transferred | $		$ 705,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets | $		$ 3,000,000,000
Retail branch locations | bank_branch		9
Consolidated Total Assets Proforma Upon Acquisition | $		$ 25,000,000,000
Business Acquisition Shares Receivable By Stockholders Of Acquiree Ratio (in shares) | shares		0.5308
Business Acquisition, Share Price (in dollars per share)		$ 12.00
Common Stock par value (usd per share)		$ 51.72
Business Acquisition, Purchase Price Allocation | $		$ 39.45