Issuance of Common Stock (Details) - USD ($)		9 Months Ended
	Mar. 28, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Equity [Abstract]
Common stock shares issued (in shares)	5,175,000	50,194,000		44,645,000
Proceeds from issuance of common stock	$ 136,600,000	$ 143,069,000	$ 4,422,000
Underwriting discounts and commissions	8,800,000
Other direct costs incurred	$ 816,000	$ 816,000	$ 0