CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Cash paid for capitalized interest	$ 13,509	$ 21,109	$ 16,447
Payments of stock issuance costs	$ 0	$ 92,838	$ 1,150