Quarterly report pursuant to Section 13 or 15(d)

Acquisitions (Narrative) (Details)

v3.7.0.1
Acquisitions (Narrative) (Details)
$ / shares in Units, shares in Millions
 2 Months Ended 3 Months Ended 6 Months Ended
Feb. 17, 2017
USD ($)
a
$ / shares
shares
Feb. 16, 2017
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Dec. 15, 2016
$ / shares
Business Acquisition [Line Items]              
Acquisition expense     $ 1,060,000 $ 0 $ 2,358,000 $ 0  
Share price (in dollars per share) | $ / shares $ 19.48           $ 20.96
Vitruvian acquisition              
Business Acquisition [Line Items]              
Net surface area | a 46,400            
Total consideration $ 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 expense     $ 1,100,000   $ 2,400,000    
Goodwill $ 0            
Bargain purchase gain $ 0            
Business acquisition, share price (in dollars per share) | $ / shares             $ 20.96
Decrease in fair value of shares issued for acquisition, amount   $ 35,300,000          
Indemnity escrow | Vitruvian acquisition              
Business Acquisition [Line Items]              
Equity interest issued or issuable, number of shares (in shares) | shares 5.2