Loans - Non-Covered Loan Portfolio by Credit Quality Indicator (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	$ 32,232,581		$ 29,821,715
Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	22,862,495		20,699,927
Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	7,660,776		7,364,231
One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	404,750		560,730
Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	310,585		344,100
Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	31,238,606		28,968,988
Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	960,019	[1],[2]	813,691	[1],[3]
Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	33,956		39,036
Total Other Loan Segment
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	993,975		852,727
Pass | Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	22,799,073		20,527,460
Pass | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	7,611,591		7,304,502
Pass | One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	398,617		554,132
Pass | Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	307,918		333,805
Pass | Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	31,117,199		28,719,899
Pass | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	910,114	[1]	793,693	[1]
Pass | Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	32,808		37,688
Pass | Total Other Loan Segment
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	942,922		831,381
Special Mention | Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	27,104		73,549
Special Mention | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	13,636		25,407
Special Mention | Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans			7,400
Special Mention | Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	40,740		106,356
Special Mention | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	40,957	[1]	13,036	[1]
Special Mention | Total Other Loan Segment
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	40,957		13,036
Substandard | Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	36,318		98,918
Substandard | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	35,549		33,822
Substandard | One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	6,133		6,598
Substandard | Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	2,667		2,895
Substandard | Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	80,667		142,233
Substandard | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	8,948	[1]	6,808	[1]
Substandard | Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	1,148		1,348
Substandard | Total Other Loan Segment
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	10,096		8,156
Doubtful | Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0		0
Doubtful | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0		500
Doubtful | One-to-four family
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0		0
Doubtful | Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0		0
Doubtful | Mortgage Receivable
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0		500
Doubtful | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0	[1]	154	[1]
Doubtful | Other
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	0		0
Doubtful | Total Other Loan Segment
Financing Receivable, Recorded Investment [Line Items]
Non-Covered Loans	$ 0		$ 154

[1] Includes lease financing receivables, all of which were classified as “pass.”

[2] Includes lease financing receivables, all of which were current at September 30, 2014.

[3] Includes lease financing receivables, all of which were current at December 31, 2013.