Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Schedule of share activity

The following table summarizes the share activity for Holdings:

	For the Year Ended December 31,
	2015	2016	2017
	(in thousands)
Restricted stock granted	1,385	1,426	1,598
Common stock issued through stock option exercise	183	202	227
Unvested restricted stock forfeitures	304	82	27
Stock repurchases for satisfaction of tax obligations	183	232	280