Parent Only Statements - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 250,327	$ 274,284	$ 193,785
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Interest income on tax indemnification receivable	(12,283)	(5,398)	(5,904)
Decrease in tax indemnification receivable	59,633	59,633	44,724
Increase in other assets	(47,162)	(18,070)	(24,959)
Decrease in income taxes payable, net	(18,997)	56,813	(221,222)
Increase (decrease) in payable due to entity that is a subsidiary of Navient	553	(6,774)	8,764
Increase in other liabilities	14,562	(14,731)	(2,652)
Total adjustments	(451,259)	(365,487)	(630,558)
Total net cash used in operating activities	(200,932)	(91,203)	(436,773)
Cash flows from investing activities:
Net cash provided by (used in) investing activities	(3,331,041)	(1,847,509)	(1,388,371)
Cash flows from financing activities:
Special cash contribution from Navient	0	0	472,718
Excess tax (expense) benefit from exercise of stock-based awards	(1,650)	6,140	3,271
Preferred stock dividends paid	(21,204)	(19,595)	(12,933)
Net cash (used in) provided by financing activities	3,034,547	1,995,151	2,002,059
Net (decrease) increase in cash and cash equivalents	(497,426)	56,439	176,915
Cash and cash equivalents at beginning of year	2,416,219	2,359,780	2,182,865
Cash and cash equivalents at end of year	1,918,793	2,416,219	2,359,780
Parent Company
Cash flows from operating activities:
Net income	250,327	274,284	193,785
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Undistributed earnings of subsidiaries	(265,278)	(295,638)	(211,479)
Interest income on tax indemnification receivable	(12,283)	(5,398)	(5,904)
Decrease (increase) in investment in subsidiaries, net	63,222	(103,602)	278,365
Decrease in tax indemnification receivable	59,633	59,633	44,724
(Increase) decrease in due from subsidiaries, net	(10,438)	11,012	(32,408)
Increase in other assets	(8,972)	(14,366)	(5,447)
Decrease in income taxes payable, net	(53,465)	(54,907)	(312,770)
Increase (decrease) in payable due to entity that is a subsidiary of Navient	553	(6,774)	8,764
Increase in other liabilities	8,856	1,402	14,398
Total adjustments	(218,172)	(408,638)	(221,757)
Total net cash used in operating activities	32,155	(134,354)	(27,972)
Cash flows from investing activities:
Net cash provided by (used in) investing activities	0	0	0
Cash flows from financing activities:
Special cash contribution from Navient	0	0	472,718
Excess tax (expense) benefit from exercise of stock-based awards	(710)	1,740	2,432
Preferred stock dividends paid	(21,204)	(19,595)	(12,933)
Net cash (used in) provided by financing activities	(21,914)	(17,855)	462,217
Net (decrease) increase in cash and cash equivalents	10,241	(152,209)	434,245
Cash and cash equivalents at beginning of year	282,036	434,245	0
Cash and cash equivalents at end of year	$ 292,277	$ 282,036	$ 434,245