Issuance of Common Stock (Details) - USD ($)		6 Months Ended
	Mar. 28, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Equity [Abstract]
Common stock shares issued (in shares)	5,175,000	50,092,000		44,645,000
Proceeds from issuance of common stock	$ 136,600,000	$ 140,989,000	$ 791,000
Underwriting discounts and commissions	8,800,000
Other direct costs incurred	$ 815,000	$ 815,000	$ 0