Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Securities
Available-for-sale, amortized cost	$ 393,640	$ 414,457
Available-for-sale, Gross Unrealized Gains	4,407	1,904
Available-for-sale, Gross Unrealized Losses	(5,608)	(14,671)
Total available-for-sale securities	392,439	401,690
Held-to-maturity, amortized cost	1,960,930	1,849,526
Held-to-maturity, Gross Unrealized Gains	16,946	13,023
Held-to-maturity, Gross Unrealized Losses	(27,254)	(51,427)
Held-to-maturity, estimated fair value	1,950,622	1,811,122
Residential mortgage-backed securities
Securities
Available-for-sale, amortized cost	294,947	315,767
Available-for-sale, Gross Unrealized Gains	4,407	1,904
Available-for-sale, Gross Unrealized Losses	(2,390)	(7,137)
Total available-for-sale securities	296,964	310,534
Held-to-maturity, amortized cost	1,772,334	1,760,812
Held-to-maturity, Gross Unrealized Gains	16,289	13,023
Held-to-maturity, Gross Unrealized Losses	(24,427)	(44,024)
Held-to-maturity, estimated fair value	1,764,196	1,729,811
Residential MBS GSE issuance REMICs
Securities
Available-for-sale, amortized cost	274,136	292,131
Available-for-sale, Gross Unrealized Gains	3,834	1,077
Available-for-sale, Gross Unrealized Losses	(2,384)	(7,134)
Total available-for-sale securities	275,586	286,074
Held-to-maturity, amortized cost	1,495,672	1,474,506
Held-to-maturity, Gross Unrealized Gains	14,526	12,877
Held-to-maturity, Gross Unrealized Losses	(19,594)	(33,925)
Held-to-maturity, estimated fair value	1,490,604	1,453,458
Non-GSE issuance REMICs and CMOs
Securities
Available-for-sale, amortized cost	6,427	7,516
Available-for-sale, Gross Unrealized Gains	47	57
Available-for-sale, Gross Unrealized Losses	(1)	(1)
Total available-for-sale securities	6,473	7,572
Held-to-maturity, amortized cost	3,040	3,833
Held-to-maturity, Gross Unrealized Gains	45	61
Held-to-maturity, Gross Unrealized Losses	(7)	(10)
Held-to-maturity, estimated fair value	3,078	3,884
GSE pass-through certificates
Securities
Available-for-sale, amortized cost	14,384	16,120
Available-for-sale, Gross Unrealized Gains	526	770
Available-for-sale, Gross Unrealized Losses	(5)	(2)
Total available-for-sale securities	14,905	16,888
Held-to-maturity, amortized cost	273,622	282,473
Held-to-maturity, Gross Unrealized Gains	1,718	85
Held-to-maturity, Gross Unrealized Losses	(4,826)	(10,089)
Held-to-maturity, estimated fair value	270,514	272,469
Multifamily MBS GSE issuance REMICs
Securities
Held-to-maturity, amortized cost	97,108
Held-to-maturity, Gross Unrealized Gains	580
Held-to-maturity, Gross Unrealized Losses	(52)
Held-to-maturity, estimated fair value	97,636
Obligations of GSEs
Securities
Available-for-sale, amortized cost	98,678	98,675
Available-for-sale, Gross Unrealized Losses	(3,206)	(7,522)
Total available-for-sale securities	95,472	91,153
Held-to-maturity, amortized cost	90,932	88,128
Held-to-maturity, Gross Unrealized Gains	77
Held-to-maturity, Gross Unrealized Losses	(2,775)	(7,403)
Held-to-maturity, estimated fair value	88,234	80,725
Fannie Mae stock
Securities
Available-for-sale, amortized cost	15	15
Available-for-sale, Gross Unrealized Losses	(12)	(12)
Total available-for-sale securities	3	3
Other
Securities
Held-to-maturity, amortized cost	556	586
Held-to-maturity, estimated fair value	$ 556	$ 586