Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Balance at Dec. 31, 2015	$ 782,854	$ 783	$ 916,959	$ (111,696)	$ (23,192)
Balance, Shares at Dec. 31, 2015		78,311
Net loss	(52,364)			(52,364)
Other comprehensive income, net of tax	333				333
Capital contributions and issuance of common stock	1,916	$ 1	1,915
Capital contributions and issuance of common stock, Shares		114
Equity-based compensation	2,772		2,772
Repurchase of common stock and distributions	(30,305)	$ (13)	(30,292)
Repurchase of common stock, Shares		(1,367)
Balance at Dec. 31, 2016	705,206	$ 771	891,354	(164,060)	(22,859)
Balance, Shares at Dec. 31, 2016		77,058
Net loss	(13,955)			(13,955)
Other comprehensive income, net of tax	2,275				2,275
Capital contributions and issuance of common stock	125	$ 1	124
Capital contributions and issuance of common stock, Shares		69
Equity-based compensation	3,839		3,839
Repurchase of common stock and distributions	(1,229)	$ (1)	(1,228)
Repurchase of common stock, Shares		(44)
Balance at Sep. 30, 2017	696,261	$ 771	894,089	(178,015)	(20,584)
Balance, Shares at Sep. 30, 2017		77,083
Net loss	(15,087)			(15,087)
Other comprehensive income, net of tax	13,624				13,624
Capital contributions and issuance of common stock	506,656	$ 276	506,380
Capital contributions and issuance of common stock, Shares		27,497
Equity-based compensation	28,795		28,795
Repurchase of common stock and distributions	(2,922)	$ (2)	(2,920)
Repurchase of common stock, Shares		(110)
Reclassification of effects of tax reform enactment				3,466	(3,466)
Balance at Sep. 30, 2018	$ 1,227,327	$ 1,045	$ 1,426,344	$ (189,636)	$ (10,426)
Balance, Shares at Sep. 30, 2018		104,470