Summary of Significant Accounting Policies - Reclassifications (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
General and administrative	$ 32,992	$ 31,309	$ 24,716
Acquisition and pursuit costs	2,180	4,496	2,209
Total		35,805	26,925
Depreciation		0	0
Amortization		0	0
Depreciation and amortization	142,472	127,690	116,614
Total		127,690	116,614
Cash flows used in financing activities	31,390	136,957	(87,618)
Cash flows provided by operating activities	$ 179,766	151,272	153,983
As Previously Reported
Property, Plant and Equipment [Line Items]
General and administrative		35,805	26,925
Acquisition and pursuit costs		0	0
Total		35,805	26,925
Depreciation		116,483	106,530
Amortization		11,207	10,084
Depreciation and amortization		0	0
Total		$ 127,690	116,614
Cash flows used in financing activities			(94,010)
Cash flows provided by operating activities			$ 160,375