Available-for-Sale Securities (Tables)

9 Months Ended

Sep. 30, 2013

Schedule of Available-for-sale Securities [Line Items]

Schedule of Available-for-sale Securities Reconciliation [Table Text Block]

Available-for-sale securities as of September 30, 2013 were as follows (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Debentures
U.S. government-guaranteed obligations	$	54,564	$	62	$	108	$	54,518
Government-sponsored enterprises	5,023,165		4,570		6,440		5,021,295
Other	441,137		360		1,231		440,266
Total	$	5,518,866	$	4,992	$	7,779	$	5,516,079

Available-for-sale securities as of December 31, 2012 were as follows (in thousands):

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
Debentures
U.S. government-guaranteed obligations	$	56,119	$	301	$	3	$	56,417
Government-sponsored enterprises	5,236,358		22,280		644		5,257,994
Other	457,149		867		274		457,742
Total	$	5,749,626	$	23,448	$	921	$	5,772,153

Categories of Investments, Marketable Securities, Available-for-sale Securities [Member]

Schedule of Available-for-sale Securities [Line Items]

Schedule of Unrealized Loss on Investments [Table Text Block]

The following table summarizes (in thousands, except number of positions) the available-for-sale securities with unrealized losses as of September 30, 2013. The unrealized losses are aggregated by major security type and length of time that individual securities have been in a continuous loss position.

	Less than 12 Months					12 Months or More					Total
	Number of Positions	Estimated Fair Value		Gross Unrealized Losses		Number of Positions	Estimated Fair Value		Gross Unrealized Losses		Number of Positions	Estimated Fair Value		Gross Unrealized Losses
Debentures
U.S. government-guaranteed obligations	3	$	35,198	$	108	—	$	—	$	—	3	$	35,198	$	108
Government-sponsored enterprises	119	2,134,921		6,440		—	—		—		119	2,134,921		6,440
Other	23	242,636		1,122		3	14,850		109		26	257,486		1,231
Total	145	$	2,412,755	$	7,670	3	$	14,850	$	109	148	$	2,427,605	$	7,779

The following table summarizes (in thousands, except number of positions) the available-for-sale securities with unrealized losses as of December 31, 2012. The unrealized losses are aggregated by major security type and length of time that individual securities have been in a continuous loss position.

	Less than 12 Months					12 Months or More					Total
	Number of Positions	Estimated Fair Value		Gross Unrealized Losses		Number of Positions	Estimated Fair Value		Gross Unrealized Losses		Number of Positions	Estimated Fair Value		Gross Unrealized Losses
Debentures
U.S. government-guaranteed obligations	1	$	11,340	$	3	—	$	—	$	—	1	$	11,340	$	3
Government-sponsored enterprises	23	448,123		629		1	2,373		15		24	450,496		644
Other	18	141,151		274		—	—		—		18	141,151		274
Total	42	$	600,614	$	906	1	$	2,373	$	15	43	$	602,987	$	921

Investments Classified by Contractual Maturity Date [Table Text Block]

The amortized cost and estimated fair value of available-for-sale securities by contractual maturity at September 30, 2013 and December 31, 2012 are presented below (in thousands).

	September 30, 2013				December 31, 2012
Maturity	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Debentures
Due in one year or less	$	5,016	$	5,019	$	—	$	—
Due after one year through five years	3,871,921		3,874,920		3,340,880		3,349,030
Due after five years through ten years	1,641,929		1,636,140		2,401,976		2,416,299
Due after ten years	—		—		6,770		6,824
Total	$	5,518,866	$	5,516,079	$	5,749,626	$	5,772,153

Schedule of Interest Rate Payment Terms For Investments [Table Text Block]

The following table provides interest rate payment terms for investment securities classified as available-for-sale at September 30, 2013 and December 31, 2012 (in thousands):

	September 30, 2013		December 31, 2012
Amortized cost of available-for-sale securities
Fixed-rate	$	5,443,866	$	5,674,626
Variable-rate	75,000		75,000
Total	$	5,518,866	$	5,749,626