Summary of Significant Accounting Policies - Basic and Diluted Net Income Per Share Calculations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic net income per common share calculation:
Net income available to common shareholders	$ 121,630	$ 28,356
Denominator - Weighted average common shares outstanding (in shares)	75,372,883	75,803,402
Basic net income per common share (in dollars per share)	$ 1.61	$ 0.37
Diluted net income per common share calculation:
Numerator – Net income available to common shareholders	$ 121,630	$ 28,356
Denominator - Weighted average common shares outstanding (in shares)	75,373,000	75,803,000
Dilutive shares contingently issuable (in shares)	284,000	163,000
Weighted average diluted common shares outstanding (in shares)	75,657,149	75,966,295
Diluted net income per common share (in dollars per share)	$ 1.61	$ 0.37