Business Combinations (Details) $ in Thousands, shares in Millions		3 Months Ended		9 Months Ended
	Dec. 01, 2019 USD ($) office shares	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Loans		$ 32,090,554		$ 32,090,554	$ 29,537,449
Oritani
Business Acquisition [Line Items]
Assets	$ 4,300,000
Loans	3,400,000
Deposits	$ 2,900,000
Number of branches | office	26
Conversion ratio for shares issued	1.60
Consideration transferred	$ 835,300
Shares issued in connection with acquisition (in shares) | shares	71.1
Merger expenses		$ 106		$ 1,800
Goodwill increase			$ 1,800