Loans Receivable and Allowance for Loan Losses (Residential Mortgage, Consumer and Other Loans, by Class and Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Recorded Investment
Total	$ 11,469,608	$ 11,909,722
Past due 90 days or more	66,155	62,834
Consumer and Other Loans
Recorded Investment
Total	243,481	249,368
Past due 90 days or more	6,243	6,040
Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Total	172,127	184,553
Past due 90 days or more	6,243	6,040
Consumer and Other Loans | Commercial and industrial
Recorded Investment
Total	71,354	64,815
Past due 90 days or more		0
Mortgage loans (gross)
Recorded Investment
Total	11,226,127	11,660,354
Past due 90 days or more	59,912	56,794
Mortgage loans (gross) | Residential Mortgage Loans
Recorded Investment
Total	6,420,234	6,873,536
Past due 90 days or more	52,268	44,989
Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Total	663,937	854,182
Past due 90 days or more	12,338	11,502
Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Total	4,800,026	5,003,693
Past due 90 days or more	21,020	14,355
Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Total	510,044	611,008
Past due 90 days or more	13,513	16,289
Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Total	446,227	404,653
Past due 90 days or more	5,397	2,843
Performing | Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Total	165,741	178,513
Performing | Consumer and Other Loans | Commercial and industrial
Recorded Investment
Total	71,354	64,815
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Total	639,083	826,155
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Total	4,768,043	4,981,880
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Total	472,242	568,424
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Total	436,652	396,922
Non-performing: | Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Current or past due less than 90 days	143	0
Past due 90 days or more	6,243	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	12,516	16,525
Past due 90 days or more	12,338	11,502
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Current or past due less than 90 days	10,963	7,458
Past due 90 days or more	21,020	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	24,289	26,295
Past due 90 days or more	13,513	16,289
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Current or past due less than 90 days	4,178	4,888
Past due 90 days or more	$ 5,397	$ 2,843