Loans Receivable and Allowance for Loan Losses (Residential Mortgage, Consumer and Other Loans, by Class and Credit Quality Indicator) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Recorded Investment
Total	$ 11,775,840	$ 11,909,722
Past due 90 days or more	55,504	62,834
Consumer and Other Loans
Recorded Investment
Total	253,085	249,368
Past due 90 days or more	6,691	6,040
Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Total	178,191	184,553
Past due 90 days or more	6,691	6,040
Consumer and Other Loans | Commercial and industrial
Recorded Investment
Total	74,894	64,815
Past due 90 days or more	0	0
Mortgage loans (gross)
Recorded Investment
Total	11,522,755	11,660,354
Past due 90 days or more	48,813	56,794
Mortgage loans (gross) | Residential Mortgage Loans
Recorded Investment
Total	6,660,900	6,873,536
Past due 90 days or more	46,749	44,989
Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Total	755,660	854,182
Past due 90 days or more	11,278	11,502
Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Total	4,917,892	5,003,693
Past due 90 days or more	16,478	14,355
Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Total	566,589	611,008
Past due 90 days or more	14,231	16,289
Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Total	420,759	404,653
Past due 90 days or more	4,762	2,843
Performing | Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Total	171,355	178,513
Performing | Consumer and Other Loans | Commercial and industrial
Recorded Investment
Total	74,894	64,815
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation interest-only
Recorded Investment
Total	730,927	826,155
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Total	4,890,730	4,981,880
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation interest-only loans
Recorded Investment
Total	526,666	568,424
Performing | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Total	413,447	396,922
Non-performing: | Consumer and Other Loans | Home equity and other consumer
Recorded Investment
Current or past due less than 90 days	145	0
Past due 90 days or more	6,691	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	13,455	16,525
Past due 90 days or more	11,278	11,502
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Full documentation amortizing loans
Recorded Investment
Current or past due less than 90 days	10,684	7,458
Past due 90 days or more	16,478	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	25,692	26,295
Past due 90 days or more	14,231	16,289
Non-performing: | Mortgage loans (gross) | Residential Mortgage Loans | Reduced documentation amortizing loans
Recorded Investment
Current or past due less than 90 days	2,550	4,888
Past due 90 days or more	$ 4,762	$ 2,843