Stockholders' Equity and EPS - Reconciliation of Basic EPS to Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income available to common stockholders	$ 441,713	$ 267,281	$ 802,901	$ 874,000
Denominator:
Weighted average common shares outstanding-basic (in shares)	51,773	51,545	51,640	52,025
Weighted average common shares outstanding—diluted (in shares)	52,146	51,858	51,950	52,431
Earnings per common share:
Basic (dollars per share)	$ 8.53	$ 5.19	$ 15.55	$ 16.80
Diluted (dollars per share)	$ 8.47	$ 5.15	$ 15.46	$ 16.67
Stock options and ESPP
Denominator:
Weighted average effect of dilutive securities (in shares)	141	203	147	238
Restricted stock units and awards
Denominator:
Weighted average effect of dilutive securities (in shares)	232	110	163	168