Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Numerator [Abstract]
Net income attributable to CAI common stockholders used in the calculation of basic and diluted earnings per share	$ 15,135	$ 10,880	$ 29,526	$ 23,676
Denominator [Abstract]
Weighted average shares used in the calculation of basic earnings per share (in shares)	19,295,000	19,295,000	19,295,000	19,295,000
Effect of dilutive securities (in shares)	424,000	503,000	417,000	484,000
Weighted average shares used in the calculation of diluted earnings per share (in shares)	19,719,000	19,798,000	19,712,000	19,779,000
Net income per share attributable to CAI common stockholders [Abstract]
Basic (in dollars per share)	$ 0.78	$ 0.56	$ 1.53	$ 1.23
Diluted (in dollars per share)	$ 0.77	$ 0.55	$ 1.50	$ 1.20
Stock options having antidilutive effect (in shares)	371,000	220,000	371,000	220,000