Accumulated Other Comprehensive Loss (Summary of Activity in Accumulated Other Comprehensive Loss attributable to Navigant, Consulting Inc.) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance			$ 708,564
Balance	$ 651,041		651,041
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	(6,971)	$ (17,939)	(6,529)	$ (19,308)
Unrealized gain (loss)	1,042	(3,406)	600	(2,037)
Balance	(5,929)	(21,345)	(5,929)	(21,345)
Accumulated Net Loss from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance		387		130
Unrealized gain (loss)		112		362
Reclassified to interest expense		(54)		(44)
Income tax expense		15		12
Balance		460		460
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance	$ (5,929)	$ (20,885)	$ (5,929)	$ (20,885)