EARNINGS PER SHARE AND STOCKHOLDERS' EQUITY - Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Calculation of basic EPS
Walker and Dunlop net income	$ 42,916	$ 44,043	$ 42,196	$ 44,218	$ 45,750	$ 37,716	$ 41,112	$ 36,861	$ 173,373	$ 161,439	$ 211,127
Less: dividends and undistributed earnings allocated to participating securities									5,649	5,790	8,443
Net income applicable to common stockholders									$ 167,724	$ 155,649	$ 202,684
Basic weighted average shares outstanding									29,913	30,202	30,176
Basic EPS	$ 1.38	$ 1.42	$ 1.36	$ 1.44	$ 1.47	$ 1.20	$ 1.31	$ 1.18	$ 5.61	$ 5.15	$ 6.72
Calculation of diluted EPS
Add: reallocation of dividends and undistributed earnings based on assumed conversion									$ 126	$ 170	$ 313
Net income allocated to common stockholders									$ 167,850	$ 155,819	$ 202,997
Add: weighted-average diluted non-participating securities									902	1,182	1,210
Weighted average diluted shares outstanding									30,815	31,384	31,386
Diluted EPS	$ 1.34	$ 1.39	$ 1.33	$ 1.39	$ 1.41	$ 1.15	$ 1.26	$ 1.14	$ 5.45	$ 4.96	$ 6.47