Basic and Diluted Earnings Per Share (EPS) Data Numerator and Denominator Calculation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share, Basic and Diluted [Abstract]
Net income (loss) attributable to CDI	$ 4,992	$ 5,349	$ 4,952	$ 3,823	$ (657)	$ 2,814	$ 11,982	$ 694	$ 19,116	$ 14,833	$ (10,858)
Basic weighted-average shares (in shares)									19,344,000	19,144,000	19,015,000
Dilutive effect o stock-based awards (in shares)									401,000	212,000	0
Diluted weighted-average shares (in shares)									19,745,000	19,356,000	19,015,000
Basic (in dollars per share)	$ 0.26	$ 0.27	$ 0.26	$ 0.20	$ (0.03)	$ 0.15	$ 0.62	$ 0.04	$ 0.99	$ 0.77	$ (0.57)
Diluted (in dollars per share)	$ 0.25	$ 0.27	$ 0.25	$ 0.20	$ (0.03)	$ 0.15	$ 0.62	$ 0.04	$ 0.97	$ 0.77	$ (0.57)
Shares excluded from computation of EPS (in shares)									425,000	729,000	1,259,000