Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation, Common Stock Repurchases and Dividends Schedule of Assumptions (Details)

v2.4.1.9
Stock-Based Compensation, Common Stock Repurchases and Dividends Schedule of Assumptions (Details) (Stock Options)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected life of options (in years) 4 years 9 months   4 years 9 months
Minimum risk free interest rate 1.36%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum 0.34%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum 0.59%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
Maximum risk free interest rate 1.61%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum 1.34%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum 0.94%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
Expected minimum volatility rate 33.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum 31.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum 43.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
Expected maximum volatility rate 34.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum 43.70%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum 46.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
Minimum
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected life of options (in years)   2 years  
Expected dividend yield 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Maximum
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Expected life of options (in years)   4 years 9 months  
Expected dividend yield 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
9.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember