Securities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities
Available-for-sale, Less Than Twelve Months, Estimated Fair Value	$ 301	$ 334,474
Available-for-sale, Less Than Twelve Months, Gross Unrealized Losses	(4)	(14,657)
Available-for-sale, Twelve Months or Longer, Estimated Fair Value	220,079	205
Available-for-sale, Twelve Months or Longer, Gross Unrealized Losses	(5,604)	(14)
Available-for-sale, Total, Estimated Fair Value	220,380	334,679
Available-for-sale, Total, Gross Unrealized Losses	(5,608)	(14,671)
Held-to-maturity, Less Than Twelve Months, Estimated Fair Value	226,752	1,031,627
Held-to-maturity, Less Than Twelve Months, Gross Unrealized Losses	(1,637)	(43,112)
Held-to-maturity, Twelve Months or Longer, Estimated Fair Value	753,662	151,609
Held-to-maturity, Twelve Months or Longer, Gross Unrealized Losses	(25,617)	(8,315)
Held-to-maturity, Total, Estimated Fair Value	980,414	1,183,236
Held-to-maturity, Total, Gross Unrealized Losses	(27,254)	(51,427)
Residential MBS GSE issuance REMICs
Securities
Available-for-sale, Less Than Twelve Months, Estimated Fair Value		243,149
Available-for-sale, Less Than Twelve Months, Gross Unrealized Losses		(7,134)
Available-for-sale, Twelve Months or Longer, Estimated Fair Value	124,418
Available-for-sale, Twelve Months or Longer, Gross Unrealized Losses	(2,384)
Available-for-sale, Total, Estimated Fair Value	124,418	243,149
Available-for-sale, Total, Gross Unrealized Losses	(2,384)	(7,134)
Held-to-maturity, Less Than Twelve Months, Estimated Fair Value	206,646	719,715
Held-to-maturity, Less Than Twelve Months, Gross Unrealized Losses	(1,577)	(25,611)
Held-to-maturity, Twelve Months or Longer, Estimated Fair Value	501,931	151,581
Held-to-maturity, Twelve Months or Longer, Gross Unrealized Losses	(18,017)	(8,314)
Held-to-maturity, Total, Estimated Fair Value	708,577	871,296
Held-to-maturity, Total, Gross Unrealized Losses	(19,594)	(33,925)
Non-GSE issuance REMICs and CMOs
Securities
Available-for-sale, Twelve Months or Longer, Estimated Fair Value	118	132
Available-for-sale, Twelve Months or Longer, Gross Unrealized Losses	(1)	(1)
Available-for-sale, Total, Estimated Fair Value	118	132
Available-for-sale, Total, Gross Unrealized Losses	(1)	(1)
Held-to-maturity, Less Than Twelve Months, Estimated Fair Value	299	392
Held-to-maturity, Less Than Twelve Months, Gross Unrealized Losses	(7)	(10)
Held-to-maturity, Total, Estimated Fair Value	299	392
Held-to-maturity, Total, Gross Unrealized Losses	(7)	(10)
GSE pass-through certificates
Securities
Available-for-sale, Less Than Twelve Months, Estimated Fair Value	301	172
Available-for-sale, Less Than Twelve Months, Gross Unrealized Losses	(4)	(1)
Available-for-sale, Twelve Months or Longer, Estimated Fair Value	68	70
Available-for-sale, Twelve Months or Longer, Gross Unrealized Losses	(1)	(1)
Available-for-sale, Total, Estimated Fair Value	369	242
Available-for-sale, Total, Gross Unrealized Losses	(5)	(2)
Held-to-maturity, Less Than Twelve Months, Estimated Fair Value	28	230,795
Held-to-maturity, Less Than Twelve Months, Gross Unrealized Losses	(1)	(10,088)
Held-to-maturity, Twelve Months or Longer, Estimated Fair Value	173,574	28
Held-to-maturity, Twelve Months or Longer, Gross Unrealized Losses	(4,825)	(1)
Held-to-maturity, Total, Estimated Fair Value	173,602	230,823
Held-to-maturity, Total, Gross Unrealized Losses	(4,826)	(10,089)
Multifamily MBS GSE issuance REMICs
Securities
Held-to-maturity, Less Than Twelve Months, Estimated Fair Value	19,779
Held-to-maturity, Less Than Twelve Months, Gross Unrealized Losses	(52)
Held-to-maturity, Total, Estimated Fair Value	19,779
Held-to-maturity, Total, Gross Unrealized Losses	(52)
Obligations of GSEs
Securities
Available-for-sale, Less Than Twelve Months, Estimated Fair Value		91,153
Available-for-sale, Less Than Twelve Months, Gross Unrealized Losses		(7,522)
Available-for-sale, Twelve Months or Longer, Estimated Fair Value	95,472
Available-for-sale, Twelve Months or Longer, Gross Unrealized Losses	(3,206)
Available-for-sale, Total, Estimated Fair Value	95,472	91,153
Available-for-sale, Total, Gross Unrealized Losses	(3,206)	(7,522)
Held-to-maturity, Less Than Twelve Months, Estimated Fair Value		80,725
Held-to-maturity, Less Than Twelve Months, Gross Unrealized Losses		(7,403)
Held-to-maturity, Twelve Months or Longer, Estimated Fair Value	78,157
Held-to-maturity, Twelve Months or Longer, Gross Unrealized Losses	(2,775)
Held-to-maturity, Total, Estimated Fair Value	78,157	80,725
Held-to-maturity, Total, Gross Unrealized Losses	(2,775)	(7,403)
Fannie Mae stock
Securities
Available-for-sale, Twelve Months or Longer, Estimated Fair Value	3	3
Available-for-sale, Twelve Months or Longer, Gross Unrealized Losses	(12)	(12)
Available-for-sale, Total, Estimated Fair Value	3	3
Available-for-sale, Total, Gross Unrealized Losses	$ (12)	$ (12)