Earnings per Share - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income available to common stockholders for basic and diluted net income per common share	$ 289,441	$ 207,073
Denominator:
Weighted average common shares outstanding for basic net income per common share (in shares)	4,491,362	4,710,340
Weighted average impact of dilutive equity instruments (in shares)	95,083	74,080
Weighted average shares for diluted net income per common share (in shares)	4,586,445	4,784,420
Net income per common share:
Basic (in dollars per share)	$ 0.06	$ 0.04
Diluted (in dollars per share)	$ 0.06	$ 0.04