TOTAL EQUITY - Summary of Changes in Total Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Change in Stockholders' Equity
Balances at the beginning of the period	$ 1,043,315	$ 1,042,285	$ 928,072	$ 907,192	$ 1,042,285	$ 907,192
Balance at the beginning of the period (in shares)		30,035			30,035
Walker and Dunlop net income	62,059	$ 47,829	42,196	44,218	$ 109,888	86,414
Net income (loss) from noncontrolling interests		(224)	(50)	(158)	(224)	(208)
Purchase of noncontrolling interests	(10,342)
Contributions from noncontrolling interests		675
Other comprehensive income (loss), net of tax	1,430	(1,918)	666	301
Stock-based compensation - equity classified	5,592	5,061	4,417	6,812
Issuance of common stock in connection with equity compensation plans	196	11,369	1	4,187
Repurchase and retirement of common stock	(405)	(26,737)	(1,756)	(24,159)
Cash dividends paid	(11,294)	(11,347)	(9,311)	(9,319)
Balances at the end of the period	$ 1,090,551	$ 1,043,315	$ 964,235	$ 928,072	$ 1,090,551	964,235
Balance at the end of the period (in shares)	30,369				30,369
Cash dividends paid per common share	$ 0.36	$ 0.36	$ 0.30	$ 0.30
ASU 2016-02
Change in Stockholders' Equity
Cumulative effect adjustment for adoption of ASU, net of tax				$ (1,002)
ASU 2016-13
Change in Stockholders' Equity
Cumulative effect adjustment for adoption of ASU, net of tax		$ (23,678)
Common Stock
Change in Stockholders' Equity
Balances at the beginning of the period	$ 303	$ 300	$ 300	$ 295	$ 300	$ 295
Balance at the beginning of the period (in shares)	30,330	30,035	29,973	29,497	30,035	29,497
Issuance of common stock in connection with equity compensation plans	$ 1	$ 7	$ 1	$ 9
Issuance of common stock in connection with equity compensation plans (in shares)	50	675	24	935
Repurchase and retirement of common stock		$ (4)	$ (1)	$ (4)
Repurchase and retirement of common stock (in shares)	(11)	(380)	(33)	(459)
Balances at the end of the period	$ 304	$ 303	$ 300	$ 300	$ 304	$ 300
Balance at the end of the period (in shares)	30,369	30,330	29,964	29,973	30,369	29,964
APIC
Change in Stockholders' Equity
Balances at the beginning of the period	$ 236,007	$ 237,877	$ 223,742	$ 235,152	$ 237,877	$ 235,152
Purchase of noncontrolling interests	(3,295)
Stock-based compensation - equity classified	5,592	5,061	4,417	6,812
Issuance of common stock in connection with equity compensation plans	195	11,362		4,178
Repurchase and retirement of common stock	(405)	(18,293)	(538)	(22,400)
Balances at the end of the period	238,094	236,007	227,621	223,742	238,094	227,621
AOCI
Change in Stockholders' Equity
Balances at the beginning of the period	(1,181)	737	226	(75)	737	(75)
Other comprehensive income (loss), net of tax	1,430	(1,918)	666	301
Balances at the end of the period	249	(1,181)	892	226	249	892
Retained Earnings
Change in Stockholders' Equity
Balances at the beginning of the period	801,139	796,775	698,894	666,752	796,775	666,752
Walker and Dunlop net income	62,059	47,829	42,196	44,218
Repurchase and retirement of common stock		(8,440)	(1,217)	(1,755)
Cash dividends paid	(11,294)	(11,347)	(9,311)	(9,319)
Balances at the end of the period	851,904	801,139	730,562	698,894	851,904	730,562
Retained Earnings | ASU 2016-02
Change in Stockholders' Equity
Cumulative effect adjustment for adoption of ASU, net of tax				(1,002)
Retained Earnings | ASU 2016-13
Change in Stockholders' Equity
Cumulative effect adjustment for adoption of ASU, net of tax		(23,678)
Noncontrolling Interests
Change in Stockholders' Equity
Balances at the beginning of the period	7,047	6,596	4,910	5,068	$ 6,596	5,068
Net income (loss) from noncontrolling interests		(224)	(50)	(158)
Purchase of noncontrolling interests	$ (7,047)
Contributions from noncontrolling interests		675
Balances at the end of the period		$ 7,047	$ 4,860	$ 4,910		$ 4,860