Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Narrative) (Details)

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Acquisitions (Narrative) (Details)
$ / shares in Units, shares in Millions
 2 Months Ended 3 Months Ended 4 Months Ended 6 Months Ended
Feb. 17, 2017
USD ($)
a
$ / shares
shares
Feb. 16, 2017
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Dec. 15, 2016
$ / shares
Business Acquisition [Line Items]                
Acquisition costs     $ 0 $ 1,060,000   $ 0 $ 2,358,000  
Common stock share price (in usd per share) | $ / shares $ 19.48             $ 20.96
Vitruvian acquisition                
Business Acquisition [Line Items]                
Net surface area (in acre) | a 46,400              
Total initial purchase price $ 1,850,000,000              
Payments to acquire businesses $ 1,354,093,000              
Equity interest issued or issuable, number of shares (in shares) | shares 23.9              
Acquisition costs     $ 0 1,100,000   $ 0 $ 2,400,000  
Goodwill $ 0              
Bargain purchase gain $ 0              
Initial purchase share price (in usd per share) | $ / shares               $ 20.96
Decrease in fair value of shares issued for acquisition, amount   $ 35,300,000            
Revenue       $ 51,069,000 $ 77,997,000      
Vitruvian acquisition | Indemnity escrow                
Business Acquisition [Line Items]                
Equity interest issued or issuable, number of shares (in shares) | shares 5.2