Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Valuation of financial instruments that are marked-to-market on recurring basis

The following table summarizes the valuation of our financial instruments that are marked-to-fair value on a recurring basis.

	Fair Value Measurements on a Recurring Basis
	December 31, 2018										December 31, 2017
	Level 1		Level 2			Level 3		Total			Level 1		Level 2			Level 3		Total
Assets
Available-for-sale investments	$	—	$	176,245		$	—	$	176,245		$	—	$	244,088		$	—	$	244,088
Derivative instruments	—		2,090			—		2,090			—		812			—		812
Total	$	—	$	178,335		$	—	$	178,335		$	—	$	244,900		$	—	$	244,900
Liabilities
Derivative instruments	$	—	$	(2,032	)	$	—	$	(2,032	)	$	—	$	(2,584	)	$	—	$	(2,584	)
Total	$	—	$	(2,032	)	$	—	$	(2,032	)	$	—	$	(2,584	)	$	—	$	(2,584	)

Fair values of financial assets and liabilities, including derivative financial instruments

The following table summarizes the fair values of our financial assets and liabilities, including derivative financial instruments.

	December 31, 2018						December 31, 2017
	Fair Value		Carrying Value		Difference		Fair Value		Carrying Value		Difference
Earning assets:
Loans held for investment, net:
Private Education Loans	$	22,313,419	$	20,294,843	$	2,018,576	$	19,327,044	$	17,244,830	$	2,082,214
FFELP Loans	859,185		847,889		11,296		946,213		929,159		17,054
Personal Loans	1,156,531		1,128,187		28,344		399,879		393,652		6,227
Cash and cash equivalents	2,559,106		2,559,106		—		1,534,339		1,534,339		—
Available-for-sale investments	176,245		176,245		—		244,088		244,088		—
Accrued interest receivable	1,285,842		1,191,981		93,861		967,482		967,482		—
Tax indemnification receivable	39,207		39,207		—		168,011		168,011		—
Derivative instruments	2,090		2,090		—		812		812		—
Total earning assets	$	28,391,625	$	26,239,548	$	2,152,077	$	23,587,868	$	21,482,373	$	2,105,495
Interest-bearing liabilities:
Money-market and savings accounts	$	9,370,957	$	9,390,108	$	19,151	$	8,470,209	$	8,470,209	$	—
Certificates of deposit	9,513,194		9,551,974		38,780		7,044,208		7,034,121		(10,087		)
Short-term borrowings	—		—		—		—		—		—
Long-term borrowings	4,278,931		4,284,304		5,373		3,299,871		3,275,270		(24,601		)
Accrued interest payable	61,341		61,341		—		35,363		35,363		—
Derivative instruments	2,032		2,032		—		2,584		2,584		—
Total interest-bearing liabilities	$	23,226,455	$	23,289,759	$	63,304	$	18,852,235	$	18,817,547	$	(34,688	)
Excess of net asset fair value over carrying value					$	2,215,381					$	2,070,807