Loans Receivable and Allowance for Loan Losses (Residential Mortgage, Consumer and Other Loans, by Class and Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment
Total	$ 10,965,303	$ 11,111,727
Consumer and Other Loans
Financing Receivable, Recorded Investment
Total	255,456	252,693
Consumer and Other Loans | Home Equity and Other Consumer
Financing Receivable, Recorded Investment
Total	154,645	160,819
Consumer and Other Loans | Commercial and industrial
Financing Receivable, Recorded Investment
Total	100,811	91,874
Mortgage Loans
Financing Receivable, Recorded Investment
Total	10,709,847	10,859,034
Mortgage Loans | Residential Mortgage Loans
Financing Receivable, Recorded Investment
Total	5,820,505	6,015,415
Mortgage Loans | Residential Mortgage Loans | Full documentation interest-only
Financing Receivable, Recorded Investment
Total	380,872	432,288
Mortgage Loans | Residential Mortgage Loans | Full documentation amortizing
Financing Receivable, Recorded Investment
Total	4,587,250	4,697,966
Mortgage Loans | Residential Mortgage Loans | Reduced documentation interest-only
Financing Receivable, Recorded Investment
Total	235,711	303,231
Mortgage Loans | Residential Mortgage Loans | Reduced documentation amortizing
Financing Receivable, Recorded Investment
Total	616,672	581,930
Performing | Consumer and Other Loans | Home Equity and Other Consumer
Financing Receivable, Recorded Investment
Total	149,050	154,414
Performing | Consumer and Other Loans | Commercial and industrial
Financing Receivable, Recorded Investment
Total	100,237	91,171
Performing | Mortgage Loans | Residential Mortgage Loans | Full documentation interest-only
Financing Receivable, Recorded Investment
Total	361,616	413,913
Performing | Mortgage Loans | Residential Mortgage Loans | Full documentation amortizing
Financing Receivable, Recorded Investment
Total	4,540,065	4,653,437
Performing | Mortgage Loans | Residential Mortgage Loans | Reduced documentation interest-only
Financing Receivable, Recorded Investment
Total	211,546	275,659
Performing | Mortgage Loans | Residential Mortgage Loans | Reduced documentation amortizing
Financing Receivable, Recorded Investment
Total	576,499	552,070
Non-performing | Consumer and Other Loans | Home Equity and Other Consumer | Current or past due less than 90 days
Financing Receivable, Recorded Investment
Total	0	0
Non-performing | Consumer and Other Loans | Home Equity and Other Consumer | Past due 90 days or more
Financing Receivable, Recorded Investment
Total	5,595	6,405
Non-performing | Consumer and Other Loans | Commercial and industrial | Current or past due less than 90 days
Financing Receivable, Recorded Investment
Total	0	0
Non-performing | Consumer and Other Loans | Commercial and industrial | Past due 90 days or more
Financing Receivable, Recorded Investment
Total	574	703
Non-performing | Mortgage Loans | Residential Mortgage Loans | Full documentation interest-only | Current or past due less than 90 days
Financing Receivable, Recorded Investment
Total	6,876	7,016
Non-performing | Mortgage Loans | Residential Mortgage Loans | Full documentation interest-only | Past due 90 days or more
Financing Receivable, Recorded Investment
Total	12,380	11,359
Non-performing | Mortgage Loans | Residential Mortgage Loans | Full documentation amortizing | Current or past due less than 90 days
Financing Receivable, Recorded Investment
Total	8,568	11,662
Non-performing | Mortgage Loans | Residential Mortgage Loans | Full documentation amortizing | Past due 90 days or more
Financing Receivable, Recorded Investment
Total	38,617	32,867
Non-performing | Mortgage Loans | Residential Mortgage Loans | Reduced documentation interest-only | Current or past due less than 90 days
Financing Receivable, Recorded Investment
Total	9,531	12,287
Non-performing | Mortgage Loans | Residential Mortgage Loans | Reduced documentation interest-only | Past due 90 days or more
Financing Receivable, Recorded Investment
Total	14,634	15,285
Non-performing | Mortgage Loans | Residential Mortgage Loans | Reduced documentation amortizing | Current or past due less than 90 days
Financing Receivable, Recorded Investment
Total	16,169	15,538
Non-performing | Mortgage Loans | Residential Mortgage Loans | Reduced documentation amortizing | Past due 90 days or more
Financing Receivable, Recorded Investment
Total	$ 24,004	$ 14,322