Loans and Leases - Portfolio of Loans Held for Investment by Credit Quality Indicator (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 42,767,551	$ 41,844,019
Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		32,100,281	31,158,672
Multi-Family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		31,688,547	30,903,657
Multi-Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		343,366	239,664
Multi-Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		68,368	15,351
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,884,667	7,081,910
Commercial Real Estate | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		5,999,490	6,902,218
Commercial Real Estate | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		775,959	104,648
Commercial Real Estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		109,218	75,044
One-to-Four Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		274,095	380,361
One-to-Four Family | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		272,393	377,883
One-to-Four Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans			748
One-to-Four Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,702	1,730
Acquisition, Development, and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		86,007	200,596
Acquisition, Development, and Construction | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		62,589	158,751
Acquisition, Development, and Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		23,418	41,456
Acquisition, Development, and Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans			389
Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[1]	39,345,050	38,821,539
Mortgage Receivable | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		38,023,019	38,342,509
Mortgage Receivable | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		1,142,743	386,516
Mortgage Receivable | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		179,288	92,514
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2],[3]	3,416,040	3,014,378
Commercial and Industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	3,351,910	2,960,557
Commercial and Industrial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	3,892	1,588
Commercial and Industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	[2]	60,238	52,233
Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,461	8,102
Other | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		6,459	7,850
Other | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		2	252
Total Other Loans
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,422,501	3,022,480
Total Other Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,358,369	2,968,407
Total Other Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		3,892	1,588
Total Other Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans		$ 60,240	$ 52,485

[1] Excludes accrued interest receivable of $217.8 million and $116.9 million at September 30, 2020 and December 31, 2019, respectively, which is included in other assets in the Consolidated Statements of Condition.

[2] Includes lease financing receivables, all of which were classified as Pass

[3] Includes specialty finance loans and leases of $3.1 billion and $2.6 billion, respectively, at September 30, 2020 and December 31, 2019, and other C&I loans of $394.3 million and $420.1 million, respectively, at September 30, 2020 and December 31, 2019.