Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Useful life of assets	30 years
Prepaid tax asset, net	$ 419,474,000	$ 277,496,000
Unrecognized tax benefits	0	0
Unrecognized tax benefits, income tax penalties and interest accrued	0	0
Internal Revenue Service (IRS)
Income Tax Contingency [Line Items]
Federal business tax credits	36,300,000	4,100,000
Internal Revenue Service (IRS) | Prepaid Expenses and Other Current Assets
Income Tax Contingency [Line Items]
Federal income tax refunds receivable	33,200,000	0
State
Income Tax Contingency [Line Items]
NOL carryforwards	1,100,000	1,300,000
NOL, Valuation Allowance	$ 200,000	$ 200,000
Minimum | State
Income Tax Contingency [Line Items]
Operating loss carryforwards expiration year	2029
Maximum | State
Income Tax Contingency [Line Items]
Operating loss carryforwards expiration year	2034