Quarterly Results - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Implementation of EHR applications
Quarterly Financial Information [Line Items]
Unfavorable pre-tax reduction	$ 2.8	$ 8.5	$ 8.7	$ 8.3		$ 8.0	$ 6.9	$ 8.3
Unfavorable after-tax reduction	$ 1.8	$ 5.3	$ 5.5	$ 5.2		$ 5.0	$ 4.4	$ 5.3
Tax reduction per diluted share	$ 0.02	$ 0.06	$ 0.05	$ 0.05		$ 0.05	$ 0.05	$ 0.05
EHR applications
Quarterly Financial Information [Line Items]
Tax reduction per diluted share					$ 0.03
Favorable after-tax reduction					$ 3.1
Favorable pre-tax reduction					$ 4.9