Common Stock, Preferred Stock and Equity Plans - Performance-based RSUs (PSUs) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential awards, percent of target shares, minimum	0.00%
Potential awards, percent of target shares, maximum	200.00%
Number of Units
Beginning of the period (in shares)	734
Granted (in shares)	547
Vested (in shares)	(577)
Cancelled (in shares)	(48)
End of the period (in shares)	656	734
Weighted-average Grant-date Fair Value
Beginning of the period ( in usd per share)	$ 143.21
Weighted average fair value ( in usd per share)	241.38
Vested ( in usd per share)	114.11
Cancelled ( in usd per share)	194.46
End of the period ( in usd per share)	$ 202.06	$ 143.21
Restricted stock vested in period, total fair value	$ 138.5	$ 73.3	$ 23.2
Financial performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Tranche one | Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of awards in tranche	50.00%
Performance period	1 year
Vesting period	3 years
Tranche one | Financial performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average Grant-date Fair Value	33.30%
Tranche two | Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of awards in tranche	50.00%
Performance period	3 years
Vesting period	3 years
Tranche two | Financial performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average Grant-date Fair Value	33.30%
Tranche three | Financial performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average Grant-date Fair Value	33.30%