Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator [Abstract]
Net income attributable to CAI common stockholders used in the calculation of basic and diluted earnings per share	$ 16,931	$ 15,135	$ 32,998	$ 29,526
Denominator [Abstract]
Weighted average shares used in the calculation of basic earnings per share (in shares)	22,144,000	19,295,000	22,115,000	19,295,000
Dilutive Securities Included In Computation Of Earnings Per Share [Line Items]
Weighted average shares used in the calculation of diluted earnings per share (in shares)	22,711,000	19,719,000	22,690,000	19,712,000
Net income per share attributable to CAI common stockholders [Abstract]
Basic (in dollars per share)	$ 0.76	$ 0.78	$ 1.49	$ 1.53
Diluted (in dollars per share)	$ 0.75	$ 0.77	$ 1.45	$ 1.50
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities having antidilutive effect (in shares)			271,300	371,000
Stock options [Member]
Dilutive Securities Included In Computation Of Earnings Per Share [Line Items]
Effect of dilutive securities (in shares)	567,000	424,000	575,000	417,000