Loans Receivable and Allowance for Loan Losses (Residential Mortgage, Consumer and Other Loans, by Class and Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Recorded Investment
Total	$ 11,210,370	$ 11,909,722
Past due 90 days or more	179,125	170,673
Consumer and Other Loans
Recorded Investment
Total	248,654	249,368
Past due 90 days or more	8,794	9,432
Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Total	167,067	184,553
Past due 90 days or more	8,794	9,432
Consumer and Other Loans | Commercial and industrial
Recorded Investment
Total	81,587	64,815
Past due 90 days or more		0
Mortgage loans (gross)
Recorded Investment
Total	10,961,716	11,660,354
Past due 90 days or more	170,331	161,241
Mortgage loans (gross) | Residential Mortgage Loans
Recorded Investment
Total	6,227,467	6,873,536
Past due 90 days or more	154,785	139,605
Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Total	536,231	854,182
Past due 90 days or more	25,068	35,506
Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Total	4,772,584	5,003,693
Past due 90 days or more	67,718	48,286
Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Total	396,432	611,008
Past due 90 days or more	33,808	38,636
Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Total	522,220	404,653
Past due 90 days or more	28,191	17,177
Performing | Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Total	160,858	178,513
Performing | Consumer and Other Loans | Commercial and industrial
Recorded Investment
Total	81,587	64,815
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Total	511,871	826,155
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Total	4,734,537	4,981,880
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Total	362,099	568,424
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Total	504,949	396,922
Non-performing: | Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Current or past due less than 90 days	0	0
Past due 90 days or more	6,209	6,040
Non-performing: | Consumer and Other Loans | Commercial and industrial
Recorded Investment
Past due 90 days or more	0	0
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Current or past due less than 90 days	10,339	16,525
Past due 90 days or more	14,021	11,502
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Current or past due less than 90 days	11,659	7,458
Past due 90 days or more	26,388	14,355
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Current or past due less than 90 days	18,674	26,295
Past due 90 days or more	15,659	16,289
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Current or past due less than 90 days	11,219	4,888
Past due 90 days or more	$ 6,052	$ 2,843