Earnings per Common Share - Schedule of Earnings per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Nelnet, Inc.	$ 48,100	$ 46,303	$ 28,737	$ 50,026	$ 98,346	$ 84,294	$ 26,150	$ 47,961	$ 173,166	$ 256,751	$ 267,979
Weighted average common shares outstanding - basic and diluted (in shares)									41,791,941	42,669,070	45,529,340
Earnings per share - basic and diluted (in dollars per share)	$ 1.17	$ 1.11	$ 0.68	$ 1.18	$ 2.32	$ 1.98	$ 0.61	$ 1.11	$ 4.14	$ 6.02	$ 5.89
Antidilutive securities excluded from computation of earnings per share (in shares)									0	0	0
Unvested restricted stock shareholders [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Nelnet, Inc.									$ 1,724	$ 2,688	$ 2,850
Weighted average common shares outstanding - basic and diluted (in shares)									415,977	446,735	484,141
Earnings per share - basic and diluted (in dollars per share)									$ 4.14	$ 6.02	$ 5.89
Common shareholders [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to Nelnet, Inc.									$ 171,442	$ 254,063	$ 265,129
Weighted average common shares outstanding - basic and diluted (in shares)									41,375,964	42,222,335	45,045,199
Earnings per share - basic and diluted (in dollars per share)									$ 4.14	$ 6.02	$ 5.89
Shares Issued - Deferred [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Non employee director stock, cumulative deferred shares (in shares)	171,519								171,519