Earnings per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Numerator [Abstract]
Net income attributable to CAI common stockholders used in the calculation of basic and diluted earnings per share	$ 16,067	$ 14,391
Denominator [Abstract]
Weighted average shares used in the calculation of basic earnings per share (in shares)	22,085,000	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)	22,668,000	19,704,000
Net income per share attributable to CAI common stockholders [Abstract]
Basic (in dollars per share)	$ 0.73	$ 0.75
Diluted (in dollars per share)	$ 0.71	$ 0.73
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities having antidilutive effect (in shares)	180,000	220,000
Stock options [Member]
Dilutive Securities Included In Computation Of Earnings Per Share [Line Items]
Effect of dilutive securities (in shares)	583,000	409,000