Stock-Based Compensation Plan (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing stock price (in dollars per share)	$ 24.57cap_ClosingStockPrice
2007 Equity Incentive Plan [Member] \| Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options (in years)	4 years
Percentage of stock options vesting after one year (in hundredths)	25.00%
Percentage of stock options vesting each month following first year (in hundredths)	2.083%
2007 Equity Incentive Plan [Member] \| Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options (in years)	1 year
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense recorded	$ 0.4	$ 0.4
Remaining unamortized stock-based compensation cost	1.9
Stock-based compensation cost recognition period	2 years 6 months
Aggregate Intrinsic Value [Abstract]
Aggregate intrinsic value of options exercised	4.0	0.1
Aggregate intrinsic value of options outstanding	8.6
Employee Stock Option [Member] \| 2007 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for grant	1,721,980
Contractual term	10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of stock options (in years)	4 years
Stock-based compensation expense recorded	0.1	0.1
Remaining unamortized stock-based compensation cost	$ 0.8
Stock-based compensation cost recognition period	2 years 7 months 6 days

Closing stock price on the last trading day of the year ended.

No definition available.

Name:	cap_ClosingStockPrice
Namespace Prefix:	cap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the percentage of stock options that vest during the first year of employment.

+ References

No definition available.

+ Details

Name:	cap_PercentageOfStockOptionsVestingAfterOneYear
Namespace Prefix:	cap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of stock options that vest each month following the first year of employment until fully vested.

+ References

No definition available.

+ Details

Name:	cap_PercentageOfStockOptionsVestingEachMonthFollowingFirstYear
Namespace Prefix:	cap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share Based Compensation Arrangement By Share Based Payment Award Contractual Term

+ References

No definition available.

+ Details

Name:	cap_ShareBasedCompensationArrangementByShareBasedPaymentAwardContractualTerm
Namespace Prefix:	cap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	cap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsIntrinsicValueAbstract
Namespace Prefix:	cap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 14.F)

-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

+ Details

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

+ References

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=cap_TwoThousandAndSevenEquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: