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Goodwill and Other Intangibles - Narrative (Detail) - USD ($)
3 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2018
Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]      
Finite-lived intangible assets   $ 587,528,000 $ 639,203,000
Intangible assets, accumulated amortization   207,900,000 $ 168,800,000
Nonamortizable identifiable intangibles   0  
Impairment of nonamortizable intangible assets $ 9,200,000    
Impairment of amortizable intangible assets   $ 4,300,000