Business Acquisitions - Schedule of Pro Forma Information Combines Consolidated Results of Company and Business Acquisitions (Detail) (USD $)
In Thousands, except Per Share data, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Business Combinations [Abstract]    
Net revenue $ 643,718 $ 632,774
Net income $ 69,371 $ 68,446
Net income per common share, Basic $ 0.74 $ 0.69
Net income per common share, Diluted $ 0.73 $ 0.68
Weighted average common shares, Basic 94,231 99,076
Weighted average common shares, Diluted 95,325 100,696