Acquisitions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Oct. 20, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Common Stock, Par or Stated Value Per Share		$ 0.01				$ 0.01				$ 0.01	$ 0.01
Goodwill		$ 2,548,670				$ 2,548,670				$ 2,548,670	$ 2,548,670	$ 2,173,949
Acquisition, integration and reorganization costs		$ 128,576	$ 127,610	$ 126,510	$ 127,517	$ 127,258	$ 114,901	$ 116,164	$ 115,901	$ 1,770	$ 19,735	$ 200
CU Bancorp [Member]
Business Acquisition [Line Items]
Cash paid	$ 224,338
Assets acquired	3,500,000
Liabilities assumed	2,800,000
Goodwill	374,721
Business Combination, Consideration Transferred	670,571
Loans and leases	2,075,900
Core Deposits [Member] | CU Bancorp [Member]
Business Acquisition [Line Items]
Liabilities assumed	$ 2,700,000