Exit and Disposal Costs (Details) - USD ($) $ in Thousands		12 Months Ended		18 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Business Exit Costs		$ 5,100
Contractual Obligation	[1]	1,058,103
Scenario, Forecast [Member]
Restructuring Cost and Reserve [Line Items]
Business Exit Costs				$ 7,600
Office Space Leases [Member]
Restructuring Cost and Reserve [Line Items]
Gain (Loss) on Contract Termination		3,200
Contractual Obligation		50,100
Mid Continent Divestiture 2015 [Member]
Restructuring Cost and Reserve [Line Items]
Business Exit Costs			$ 9,300
Mid Continent Divestiture 2015 [Member] | Office Space Leases [Member]
Restructuring Cost and Reserve [Line Items]
Contractual Obligation		$ 3,800

[1] During the third quarter of 2015, the Company closed its office in Tulsa, Oklahoma. These amounts include lease payments for the Tulsa office, net of sublease income. The Company expects to receive $2.7 million of total sublease income through 2019.