Selected Quarterly Financial Information (Unaudited) (Details) (USD $)	3 Months Ended													12 Months Ended						3 Months Ended	12 Months Ended	3 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Jun. 30, 2011 Operating and Administrative Expenses [Member]	Dec. 31, 2013 Operating and Administrative Expenses [Member]	Jun. 30, 2011 Unfavorable Regulatory Action [Member] Operating and Administrative Expenses [Member]	Dec. 31, 2013 Year-End Adjustment [Member]
Selected Quarterly Financial Information [Abstract]
Revenue	$ 277,114,000		$ 277,916,000		$ 263,363,000		$ 269,466,000		$ 270,543,000	$ 279,390,000	$ 274,398,000	$ 280,627,000		$ 1,087,859,000		$ 1,104,958,000		$ 1,059,803,000
Gross profit	52,248,000		52,697,000		51,545,000		50,151,000		53,476,000	54,720,000	55,528,000	55,685,000		206,641,000		219,409,000		225,301,000
Operating and administrative expenses	42,717,000	[1],[2]	45,751,000	[1],[2]	46,303,000	[1],[2]	45,238,000	[1],[2]	45,472,000	45,711,000	47,664,000	48,296,000		180,009,000	[1],[2]	187,143,000		196,826,000
Restructuring and other related costs													8,100,000	5,716,000		0		8,100,000
Operating profit (1), (2), (3)	3,815,000	[1],[2],[3]	6,946,000	[1],[2],[3]	5,242,000	[1],[2],[3]	4,913,000	[1],[2],[3]	8,004,000	9,009,000	7,864,000	7,389,000		20,916,000	[3],[4],[5]	32,266,000	[4],[5]	20,375,000	[4],[5]
Income before income taxes	3,717,000		6,889,000		5,180,000		4,862,000		7,918,000	8,962,000	7,784,000	7,351,000		20,648,000		32,015,000		20,130,000
Net income	2,332,000		4,566,000		3,497,000		2,553,000		5,042,000	5,406,000	5,071,000	3,914,000		12,948,000		19,433,000		15,000,000
Net income attributable to CDI	2,427,000		4,528,000		3,438,000		2,491,000		4,992,000	5,349,000	4,952,000	3,823,000		12,884,000		19,116,000		14,833,000
Earnings per common share:
Basic (in dollars per share)	$ 0.13		$ 0.23		$ 0.18		$ 0.13		$ 0.26	$ 0.27	$ 0.26	$ 0.20		$ 0.66		$ 0.99		$ 0.77
Diluted (in dollars per share)	$ 0.12		$ 0.23		$ 0.17		$ 0.13		$ 0.25	$ 0.27	$ 0.25	$ 0.20		$ 0.65		$ 0.97		$ 0.77
Benefit related to settlement																				9,700,000	3,300,000	9,700,000
Fair value of contingent consideration	$ 600,000		$ 500,000		$ 400,000		$ 300,000							$ 600,000									$ 1,800,000

[1] In 2013, the Company's GETS segment recorded a $1.8 million benefit to "Operating and administrative expenses" related to the reduction of an acquisition-related earnout liability (by quarter: first $0.3 million, second $0.4 million, third $0.5 million and fourth $0.6 million.)

[2] In the fourth quarter of 2013, the Company recorded a $3.3 million benefit to "Operating and administrative expenses" related to the settlement of legal claims pursued by the Company.

[3] In the fourth quarter of 2013, the Company recorded a $5.7 million charge to "Restructuring and other related costs" related to the 2013 Restructuring Plan.

[4] In 2013 and 2011, the Company recorded pre-tax charges of $5.7 million and $8.1 million, respectively, to "Restructuring and other related costs" related to the 2013 and 2011 Restructuring Plans. The following table summarizes the amount of restructuring and other related costs recognized by reporting segment for the indicated periods: Year ended December 31, 2013 2012 2011 GETS $2,132 $— $4,467PSS 2,394 — 2,622MRI 215 — 372Corporate 975 — 639Restructuring and other related costs $5,716 $— $8,100

[5] In 2011, the Company's PSS segment recorded a $9.7 million benefit to "Operating and administrative expenses" related to the successful legal appeal of the UK OFT matter.