QUARTERLY RESULTS (UNAUDITED) - Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Unaudited selected financial data and operating information
Gains from mortgage banking activities	$ 124,166	$ 99,170	$ 102,237	$ 81,509	$ 129,458	$ 111,304	$ 102,176	$ 96,432	$ 407,082	$ 439,370	$ 367,185
Servicing fees	52,092	50,781	49,317	48,040	46,713	44,900	43,214	41,525	200,230	176,352	140,924
Total revenues	214,933	184,657	178,204	147,452	207,202	179,736	166,407	158,512	725,246	711,857	575,276
Personnel	90,828	79,776	71,426	55,273	91,120	78,469	63,516	56,172	297,303	289,277	227,491
Amortization and depreciation	36,271	36,739	35,489	33,635	33,705	32,343	32,860	32,338	142,134	131,246	111,427
Total expenses	149,603	133,998	125,234	103,561	140,442	125,040	110,325	102,389	512,396	478,196	389,495
Income from operations	65,330	50,659	52,970	43,891	66,760	54,696	56,082	56,123	212,850	233,661	185,781
Walker and Dunlop net income	$ 45,750	$ 37,716	$ 41,112	$ 36,861	$ 98,961	$ 34,378	$ 34,567	$ 43,221	$ 161,439	$ 211,127	$ 113,897
Basic EPS	$ 1.47	$ 1.20	$ 1.31	$ 1.18	$ 3.16	$ 1.09	$ 1.10	$ 1.38	$ 5.15	$ 6.72	$ 3.66
Diluted EPS	$ 1.41	$ 1.15	$ 1.26	$ 1.14	$ 3.03	$ 1.05	$ 1.06	$ 1.33	$ 4.96	$ 6.47	$ 3.57
Total originations	$ 9,353,456	$ 7,651,791	$ 6,193,023	$ 4,849,262	$ 8,312,167	$ 8,549,532	$ 6,031,636	$ 5,012,496
Servicing portfolio	$ 85,689,262	$ 80,485,634	$ 77,820,741	$ 75,836,280	$ 74,309,991	$ 70,138,557	$ 66,290,754	$ 64,384,024	$ 85,689,262	$ 74,309,991	$ 63,081,154