Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Narrative) (Details)

v3.8.0.1
Acquisitions (Narrative) (Details)
$ / shares in Units, shares in Millions
 2 Months Ended 3 Months Ended 9 Months Ended
Feb. 17, 2017
USD ($)
a
$ / shares
shares
Feb. 16, 2017
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Dec. 15, 2016
$ / shares
Business Acquisition [Line Items]              
Acquisition costs     $ 33,000 $ 0 $ 2,391,000 $ 0  
Common stock share price (in usd per share) | $ / shares $ 19.48           $ 20.96
Vitruvian acquisition              
Business Acquisition [Line Items]              
Net surface area | 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     $ 30,000   $ 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          
Vitruvian acquisition | Indemnity escrow              
Business Acquisition [Line Items]              
Equity interest issued or issuable, number of shares (in shares) | shares 5.2