Common Equity and Earnings per Share - Schedule of Weighted Average of Potential Class A Common Stock Excluded from Computation of Earnings Per Share (Detail) - Class A - shares shares in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Class of Stock
Weighted shares of potential class A stock excluded from calculation of diluted earnings per share	3,262	1,073
2025 Notes
Class of Stock
Weighted shares of potential class A stock excluded from calculation of diluted earnings per share	1,633	0
2027 Notes
Class of Stock
Weighted shares of potential class A stock excluded from calculation of diluted earnings per share	334	0
Stock Options
Class of Stock
Weighted shares of potential class A stock excluded from calculation of diluted earnings per share	1,211	1,073
RSU
Class of Stock
Weighted shares of potential class A stock excluded from calculation of diluted earnings per share	81	0
Employee Stock Purchase Plan
Class of Stock
Weighted shares of potential class A stock excluded from calculation of diluted earnings per share	3	0