Quarterly report pursuant to Section 13 or 15(d)

Per Share Data and Stockholders' Equity - Additional Information (Detail)

v2.4.1.9
Per Share Data and Stockholders' Equity - Additional Information (Detail) (Common Class A [Member])
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Common Class A [Member]
   
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive stock options excluded in computation of diluted earnings per share 0.4us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember
0.6us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember