Authorized shares of common and preferred stock and stock-based compensation plans - Schedule Of Restricted Stock Plans (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of RSUs
Number of RSUs, Granted (in shares)	909,274	872,853	1,065,154
Restricted Stock Units
Number of RSUs
Number of RSUs, outstanding, beginning balance (in shares)	3,178,536	3,152,964	2,806,201
Number of RSUs, Granted (in shares)	1,306,387	1,100,067	1,205,920
Number of RSUs, Earned (in shares)	(958,995)	(823,816)	(666,786)
Number of RSUs, Canceled (in shares)	(236,291)	(250,679)	(192,371)
Number of RSUs, outstanding, ending balance (in shares)	3,289,637	3,178,536	3,152,964
Weighted average grant price per share
Weighted average grant price, outstanding, beginning balance (in dollars per share)	$ 36.91	$ 31.07	$ 28.76
Weighted average grant price, Granted (in dollars per share)	46.76	48.42	34.57
Weighted average grant price, Earned (in dollars per share)	35.86	30.78	28.05
Weighted average grant price, Canceled (in dollars per share)	38.82	34.13	29.73
Weighted average grant price, outstanding, ending balance (in dollars per share)	$ 40.99	$ 36.91	$ 31.07