Stockholders' Equity - Reconciliation of beginning and ending common stock outstanding (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Reconciliation of the beginning and ending common stock outstanding
Balance, beginning of period (in shares)	139,487,000
Balance, end of period (in shares)	145,530,000
Common Stock
Reconciliation of the beginning and ending common stock outstanding
Balance, beginning of period (in shares)	139,487,375	134,706,154
Issuance of common stock (in shares)	5,890,468	4,637,445
Nonvested share-based awards, net of withheld shares (in shares)	151,729	143,776
Balance, end of period (in shares)	145,529,572