Allowance Accounts - Summary Of Activity In Valuation Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance, Operating Loss Carryforwards [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Adjustments			$ (20,600)
Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the beginning of period	$ 1,778	$ 350	4,735
Additions	1,206	1,778	3,275
Deductions	(232)	(350)	(7,660)
Adjustments	0	0	0
Balance at the end of period	2,752	1,778	350
Deferred Tax Asset Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at the beginning of period	3,771	1,936	23,076
Additions	2,788	0	0
Deductions	0	0	0
Adjustments	5,778	1,835	(21,140)
Balance at the end of period	$ 12,337	$ 3,771	$ 1,936