Consolidated Balance Sheets - USD ($)	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, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 30,562,000	$ 27,682,000	$ 23,537,000	$ 29,920,000	$ 30,924,000	$ 20,787,000	$ 31,606,000	$ 20,929,000	$ 30,755,000	$ 22,578,000
Accounts receivable, net of allowance for doubtful accounts of $3,534 and $2,622, respectively	205,386,000	200,799,000	206,242,000	184,713,000	182,464,000	185,659,000	188,247,000	196,251,000
Unbilled revenue	50,016,000	48,645,000	34,264,000	33,771,000	31,516,000	37,982,000	29,202,000	32,457,000
Inventories	40,694,000	54,174,000	34,558,000	36,674,000	36,448,000	52,830,000	43,528,000	42,350,000
Prepaid expenses	18,565,000	22,018,000	23,588,000	23,912,000	18,459,000	11,551,000	11,712,000	12,524,000
Other current assets	37,865,000	31,529,000	20,475,000	20,302,000	24,597,000	31,302,000	17,738,000	16,699,000
Total current assets	383,088,000	384,847,000	342,664,000	329,292,000	324,408,000	340,111,000	322,033,000	321,210,000
Property and equipment, net	36,714,000	37,212,000	36,030,000	34,000,000	32,656,000	32,279,000	33,089,000	33,208,000
Intangibles and other assets:
Goodwill	199,946,000	206,704,000	205,399,000	203,269,000	202,700,000	204,978,000	204,897,000	206,069,000	206,257,000
Intangible assets, net	27,563,000	28,745,000	29,699,000	30,452,000	31,538,000	33,476,000	34,831,000	36,577,000
Deferred income taxes	691,000	1,432,000	1,281,000	1,440,000	1,031,000	1,123,000	882,000	788,000
Other non-current assets	1,636,000	1,592,000	1,547,000	1,633,000	1,654,000	1,426,000	1,415,000	1,469,000
Total other assets	229,836,000	238,473,000	237,926,000	236,794,000	236,923,000	241,003,000	242,025,000	244,903,000
Total assets	649,638,000	660,532,000	616,620,000	600,086,000	593,987,000	613,393,000	597,148,000	599,321,000
Current liabilities:
Accounts payable	141,164,000	130,406,000	126,382,000	114,616,000	123,012,000	129,869,000	139,914,000	129,894,000
Current portion of contingent consideration	0	0	0	17,165,000	19,283,000	19,320,000	3,862,000	11,131,000
Other current liabilities	24,078,000	30,416,000	25,210,000	24,359,000	22,576,000	25,760,000	24,200,000	24,401,000
Deferred revenue	17,620,000	15,709,000	15,392,000	16,885,000	16,402,000	13,409,000	15,180,000	14,589,000
Accrued expenses	34,391,000	32,889,000	27,409,000	32,422,000	29,755,000	20,788,000	16,096,000	23,939,000
Total current liabilities	217,253,000	209,420,000	212,235,000	206,540,000	211,028,000	210,829,000	207,779,000	207,558,000
Revolving credit facility	128,398,000	149,184,000	118,658,000	113,691,000	107,468,000	133,734,000	111,566,000	118,615,000
Deferred income taxes	12,043,000	9,839,000	9,876,000	9,818,000	10,766,000	10,622,000	11,060,905	9,652,000
Other long-term liabilities	7,399,000	2,595,000	2,625,000	2,697,000	2,564,000	2,591,000	2,995,000	3,129,000
Total liabilities	365,093,000	371,038,000	343,394,000	332,746,000	331,826,000	357,776,000	348,100,000	348,142,000
Stockholders' equity:
Common stock, par value $0.0001 per share, 200,000 and 200,000 shares authorized, 64,075 and 63,391 shares issued, 54,055 and 54,088 shares outstanding, respectively	6,000	6,000	6,000	6,000	6,000	6,000	6,000	6,000
Additional paid-in capital	235,199,000	232,979,000	230,030,000	228,106,000	224,480,000	219,085,000	216,540,000	215,723,000
Treasury stock at cost, 10,020 and 9,303 shares, respectively	(55,873,000)	(54,938,000)	(59,224,000)	(54,949,000)	(49,458,000)	(51,724,000)	(51,724,000)	(52,207,000)
Accumulated other comprehensive loss	(19,229,000)	(12,922,000)	(15,090,000)	(18,970,000)	(20,949,000)	(15,668,000)	(15,467,000)	(14,077,000)
Retained earnings	124,442,000	124,369,000	117,504,000	113,147,000	108,082,000	103,918,000	99,693,000	101,734,000
Total stockholders' equity	284,545,000	289,494,000	273,226,000	267,340,000	262,161,000	255,617,000	249,048,000	251,179,000	$ 252,432,000	$ 290,260,000
Total liabilities and stockholders' equity	$ 649,638,000	$ 660,532,000	$ 616,620,000	$ 600,086,000	$ 593,987,000	$ 613,393,000	$ 597,148,000	$ 599,321,000