Stockholders' Equity - Common shares (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of the beginning and ending common stock outstanding
Balance, beginning of year (shares)	125,132,000
Balance, end of year (shares)	125,279,000	125,132,000
Common Stock [Member]
Reconciliation of the beginning and ending common stock outstanding
Balance, beginning of year (shares)	125,131,593	116,416,900	101,517,009
Issuance of common stock (shares)	26,203	8,395,607	14,063,100
Non-vested stock-based awards, net of withheld shares and forfeitures (shares)	121,659	319,086	836,791
Balance, end of year (shares)	125,279,455	125,131,593	116,416,900