Bonds and Notes payable (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of Debt

The following tables summarize the Company’s outstanding debt obligations by type of instrument:

	As of December 31, 2017
	Carrying amount			Interest rate range	Final maturity
Variable-rate bonds and notes issued in FFELP loan asset-backed securitizations:
Bonds and notes based on indices	$	20,352,045		1.47% - 3.37%	8/25/21 - 2/25/66
Bonds and notes based on auction	780,829			2.09% - 2.69%	3/22/32 - 11/26/46
Total FFELP variable-rate bonds and notes	21,132,874
FFELP warehouse facilities	335,992			1.55% / 1.56%	11/19/19 / 5/31/20
Variable-rate bonds and notes issued in private education loan asset-backed securitization	74,717			3.30%	12/26/40
Fixed-rate bonds and notes issued in private education loan asset-backed securitization	82,647			3.60% / 5.35%	12/26/40 / 12/28/43
Unsecured line of credit	10,000			2.98%	12/12/21
Unsecured debt - Junior Subordinated Hybrid Securities	20,381			5.07%	9/15/61
Other borrowings	70,516			2.44% - 3.38%	1/12/18 - 12/15/45
	21,727,127
Discount on bonds and notes payable and debt issuance costs	(370,554		)
Total	$	21,356,573

	As of December 31, 2016
	Carrying amount			Interest rate range	Final maturity
Variable-rate bonds and notes issued in FFELP loan asset-backed securitizations:
Bonds and notes based on indices	$	22,130,063		0.24% - 6.90%	6/25/21 - 9/25/65
Bonds and notes based on auction	998,415			1.61% - 2.28%	3/22/32 - 11/26/46
Total FFELP variable-rate bonds and notes	23,128,478
FFELP warehouse facilities	1,677,443			0.63% - 1.09%	9/7/18 - 12/13/19
Variable-rate bonds and notes issued in private education loan asset-backed securitization	112,582			2.60%	12/26/40
Fixed-rate bonds and notes issued in private education loan asset-backed securitization	113,378			3.60% / 5.35%	12/26/40 / 12/28/43
Unsecured line of credit	—			—	12/12/21
Unsecured debt - Junior Subordinated Hybrid Securities	50,184			4.37%	9/15/61
Other borrowings	18,355			3.38%	3/31/23 / 12/15/45
	25,100,420
Discount on bonds and notes payable and debt issuance costs	(431,930		)
Total	$	24,668,490

Schedule of Line of Credit Facilities

As of December 31, 2017, the Company had two FFELP warehouse facilities as summarized below.

	NFSLW-I		NHELP-II	Total
Maximum financing amount	$	500,000	500,000	1,000,000
Amount outstanding	189,502		146,490	335,992
Amount available	$	310,498	353,510	664,008
Expiration of liquidity provisions	September 20, 2019		May 31, 2018
Final maturity date	November 19, 2019		May 31, 2020
Maximum advance rates	92.0 - 98.0%		85.0 - 95.0%
Minimum advance rates	84.0 - 90.0%		85.0 - 95.0%
Advanced as equity support	$	9,513	12,876	22,389

Schedule of Asset-backed Securitizations

The following tables summarize the asset-backed securitization transactions completed in 2017 and 2016.

	Securitizations completed during the year ended December 31, 2017
	NSLT 2017-1		NSLT 2017-2		NSLT 2017-3	Total
Date securities issued	5/24/17		7/26/17		12/14/17
Total original principal amount	$	535,000	399,390		539,400	1,473,790
Bond discount	—		(2,002	)	—	(2,002	)
Issue price	$	535,000	397,388		539,400	1,471,788
Cost of funds:	1-month LIBOR plus 0.78%		1-month LIBOR plus 0.77%		1-month LIBOR plus 0.85%
Final maturity date	6/25/65		9/25/65		2/25/66

	Securitizations completed during the year ended December 31, 2016
	FFELP 2016-1		Private education loan 2016-A (a)						Total
			Class A-1A notes	Class A-1B notes		2016-A total
Date securities issued	10/12/16		12/21/16	12/21/16		12/21/16
Total original principal amount	$	426,000	112,582	91,378		225,960			$	651,960
Class A senior notes:
Total original principal amount	$	426,000	112,582	91,378		203,960			629,960
Bond discount	—		—	(609	)	(609		)	(609		)
Issue price	$	426,000	112,582	90,769		203,351			629,351
Cost of funds:	1-month LIBOR plus 0.80%		1-month LIBOR plus 1.75%	3.60%
Final maturity date	9/25/65		12/26/40	12/26/40
Class B subordinated notes:
Total original principal amount						$	22,000		22,000
Bond discount						(285		)	(285		)
Issue price						$	21,715		21,715
Cost of funds:						5.35		%
Final maturity date						12/28/43

(a) On June 26, 2015, the Company entered into a $275.0 million private education loan warehouse facility. The Company funded all loans that were included in this warehouse in the Private Education Loan 2016-A securitization and terminated the private education loan warehouse facility on December 21, 2016.

Schedule of TDP Notes Outstanding

A summary of the TDP notes outstanding as of December 31, 2017 is summarized below:

Issue date	Debt outstanding		Maturity date	Interest rate
December 30, 2015	$	12,000	March 31, 2023	3.38% - fixed
December 30, 2015	6,355		December 15, 2045	3.38% - fixed
October 31, 2017	1,743		March 31, 2023	1-month LIBOR plus 2.00%

Schedule of Long-term Debt Maturities

Bonds and notes outstanding as of December 31, 2017 are due in varying amounts as shown below.

2018	$	50,418
2019	189,502
2020	146,490
2021	33,410
2022	—
2023 and thereafter	21,307,307
	$	21,727,127

Schedule of Debt Repurchases

The following table summarizes the Company's repurchases of its own debt. Gains (losses) recorded by the Company from the repurchase of debt are included in "gain on sale of loans and debt repurchases, net" on the Company’s consolidated statements of income.

	Par value		Purchase price	Gain (loss)		Par value	Purchase price	Gain (loss)	Par value	Purchase price	Gain (loss)
	Year ended December 31,
	2017					2016			2015
Unsecured debt - Hybrid Securities	$	29,803	25,357	4,446		7,000	4,865	2,135	14,504	11,374	3,130
Asset-backed securities	154,407		155,951	(1,544	)	78,412	72,566	5,846	32,026	30,354	1,672
	$	184,210	181,308	2,902		85,412	77,431	7,981	46,530	41,728	4,802