Mortgage Banking Activities Mortgage Banking Activities, Loans Serviced for Others (Details) $ in Thousands	Mar. 31, 2016 USD ($)
Financing Receivable, Recorded Investment, Aging [Abstract]
Mortgage Loans Serviced For Others, Current	$ 20,010,761
Mortgage Loans Serviced For Others, 30 To 59 Days Past Due	177,549
Mortgage Loans Serviced For Others, 60 To 89 Days Past Due	46,517
Mortgage Loans Serviced For Others, Greater Than 90 Days or More Past Due	59,835
Mortgage Loans Serviced For Others	20,294,662
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Mortgage Loans Serviced For Others, Current	6,767,400
Mortgage Loans Serviced For Others, 30 To 59 Days Past Due	34,920
Mortgage Loans Serviced For Others, 60 To 89 Days Past Due	7,482
Mortgage Loans Serviced For Others, Greater Than 90 Days or More Past Due	25,224
Mortgage Loans Serviced For Others	6,835,026
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Mortgage Loans Serviced For Others, Current	6,835,689
Mortgage Loans Serviced For Others, 30 To 59 Days Past Due	29,996
Mortgage Loans Serviced For Others, 60 To 89 Days Past Due	5,252
Mortgage Loans Serviced For Others, Greater Than 90 Days or More Past Due	17,303
Mortgage Loans Serviced For Others	6,888,240
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Mortgage Loans Serviced For Others, Current	5,851,935
Mortgage Loans Serviced For Others, 30 To 59 Days Past Due	109,046
Mortgage Loans Serviced For Others, 60 To 89 Days Past Due	33,308
Mortgage Loans Serviced For Others, Greater Than 90 Days or More Past Due	15,338
Mortgage Loans Serviced For Others	6,009,627
Other Investor Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Mortgage Loans Serviced For Others, Current	555,737
Mortgage Loans Serviced For Others, 30 To 59 Days Past Due	3,587
Mortgage Loans Serviced For Others, 60 To 89 Days Past Due	475
Mortgage Loans Serviced For Others, Greater Than 90 Days or More Past Due	1,970
Mortgage Loans Serviced For Others	$ 561,769