Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	May 16, 2019	Apr. 17, 2019	Nov. 09, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)				2,526,858	146,516	11,815,748
Compensation expense	$ 22.3	$ 40.1	$ 68.7
Unrecognized compensation expense	$ 48.3
Unrecognized compensation expense, period of recognition	1 year 9 months 18 days
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Weighted average grant date fair value of performance shares granted (in dollars per share)	$ 124.48	$ 179.40	$ 132.94
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Weighted average grant date fair value of performance shares granted (in dollars per share)	$ 134.65	$ 168.86	$ 142.14