Summary of Significant Accounting Policies - Calculation of Both Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Common Share:
Net income available to common shareholders	$ 377,918	$ 297,105	$ 248,740
Basic weighted-average number of common shares outstanding (in shares)	403,754,356	337,792,270	331,258,964
Plus: Common stock equivalents (in shares)	1,291,851	2,325,538	1,434,754
Diluted weighted-average number of common shares outstanding (in shares)	405,046,207	340,117,808	332,693,718
Earnings per common share:
Basic (in USD per share)	$ 0.94	$ 0.88	$ 0.75
Diluted (in USD per share)	$ 0.93	$ 0.87	$ 0.75