QUARTERLY RESULTS (UNAUDITED) (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
Unaudited selected financial data and operating information
Gains from mortgage banking activities	$ 129,458	$ 111,304	$ 102,176	$ 96,432	$ 117,779	$ 100,630	$ 102,453	$ 46,323	$ 439,370	$ 367,185	$ 290,466
Servicing fees	46,713	44,900	43,214	41,525	39,370	37,134	32,771	31,649	176,352	140,924	114,757
Total revenues	207,202	179,736	166,407	158,512	178,391	154,786	147,858	94,241	711,857	575,276	468,198
Personnel	91,120	78,469	63,516	56,172	73,126	64,377	55,758	34,230	289,277	227,491	184,590
Amortization and depreciation	33,705	32,343	32,860	32,338	30,603	29,244	26,425	25,155	131,246	111,427	98,173
Total expenses	140,442	125,040	110,325	102,389	117,210	106,074	96,152	70,059	478,196	389,495	332,832
Income from operations	66,760	54,696	56,082	56,123	61,181	48,712	51,706	24,182	233,661	185,781	135,366
Walker and Dunlop net income	$ 98,961	$ 34,378	$ 34,567	$ 43,221	$ 36,790	$ 29,628	$ 32,021	$ 15,458	$ 211,127	$ 113,897	$ 82,128
Diluted earnings per share	$ 3.06	$ 1.06	$ 1.08	$ 1.35	$ 1.16	$ 0.96	$ 1.05	$ 0.50	$ 6.56	$ 3.65	$ 2.65
Total originations	$ 8,312,167	$ 8,549,532	$ 6,031,636	$ 5,012,496	$ 6,260,898	$ 5,032,238	$ 5,389,276	$ 2,615,700
Servicing portfolio	$ 74,492,166	$ 70,284,682	$ 66,290,754	$ 64,384,024	$ 63,081,154	$ 59,121,989	$ 57,321,824	$ 51,040,752	$ 74,492,166	$ 63,081,154	$ 50,212,264