Earnings per Share - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net income available to common stockholders for basic and diluted net income per common share	$ 275,722	$ 193,901	$ 684,904	$ 541,306
Denominator:
Weighted average common shares outstanding for basic net income per common share (in shares)	4,618,368	4,870,281	4,660,041	4,957,820
Weighted average impact of dilutive equity instruments (in shares)	86,203	49,548	74,800	47,313
Weighted average shares for diluted net income per common share (in shares)	4,704,571	4,919,829	4,734,841	5,005,133
Net income per common share:
Basic (in dollars per share)	$ 0.06	$ 0.04	$ 0.15	$ 0.11
Diluted (in dollars per share)	$ 0.06	$ 0.04	$ 0.14	$ 0.11