Debt - Revolving Credit Agreement (Details) - KCGA	Jun. 05, 2015 USD ($) debt_class borrowing_base	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Revolving Credit Facility
Line of Credit Facility [Line Items]
Number of debt instruments | debt_class	2
Term credit agreement	$ 355,000,000	$ 0	$ 0
Revolving credit facility amount	500,000,000
Increase in line of credit facility, maximum borrowing capacity	$ 145,000,000
Commitment fee percentage of average daily amount unused portion of revolving credit agreement	0.40%
Revolving Credit Facility | Other Assets
Line of Credit Facility [Line Items]
Debt issuance costs	$ 1,700,000
Revolving Credit Facility | Borrowing Base A
Line of Credit Facility [Line Items]
Percentage points added to interest rate base	1.50%
Revolving Credit Facility | Borrowing Base B
Line of Credit Facility [Line Items]
Percentage points added to interest rate base	2.50%
Swingline Facility
Line of Credit Facility [Line Items]
Revolving credit facility amount	$ 50,000,000
Number of borrowing bases | borrowing_base	2
Swingline Facility | Borrowing Base A and Borrowing Base B
Line of Credit Facility [Line Items]
Revolving credit facility amount	$ 115,000,000