Stockholders' Equity - Common Stock (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($) $ / shares shares
Shares Issued
Dividend reinvestment plan issuances (in shares) | shares		264,153
Option exercises (in shares) | shares		251
ATM Program issuances (in shares) | shares	5,015,673	6,799,978
Stock incentive plans, net of forfeitures (in shares) | shares	145,588	183,398
Totals (in shares) | shares	5,161,261	7,247,780
Average Price
Dividend reinvestment plan issuances (in dollars per share) | $ / shares		$ 72.33
Option exercises (in dollars per share)		47.81
ATM Program issuances (in dollars per share) | $ / shares	$ 74.15	$ 86.48
Gross Proceeds
Dividend reinvestment plan issuances		$ 19,105
Option exercises		12
ATM Program issuances	$ 371,937	588,072
Totals	371,937	607,189
Net Proceeds
Dividend reinvestment plan issuances		19,105
Option exercises		12
ATM Program issuances	366,464	576,196
Total	$ 366,464	$ 595,313