Business Combinations Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets acquired:
Loans	$ 29,537,449		$ 24,883,610
Goodwill	$ 1,373,625		$ 1,084,665		$ 690,637
Oritani Financial Corp.
Assets acquired:
Cash and cash equivalents		$ 22,239
Equity securities		51,382
Loans		3,380,841		$ 3,400,000
Premises and equipment		23,585
Bank owned life insurance		101,896
Accrued interest receivable		11,781
Goodwill		288,960
Other intangible assets		20,690
Other assets:
Deferred tax assets		24,707
FHLB and FRB stock		23,479
Other assets		1,988
Total other assets		50,174
Total assets acquired		4,292,319		4,300,000
Deposits:
Non-interest bearing		142,630
Savings, NOW and money market		1,596,690
Time		1,185,396
Total deposits		2,924,716		$ 2,900,000
Short-term borrowings		10,500
Long-term borrowings		430,130
Accrued expense and other liabilities		91,718
Total liabilities assumed		3,457,064
Common stock issued in acquisition		835,255
Oritani Financial Corp. | Available-for-sale securities
Assets acquired:
Investment securities		335,894
Oritani Financial Corp. | Held-to-maturity securities
Assets acquired:
Investment securities		$ 4,877