CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Accumulated depreciation	$ 347,882	$ 276,197
Accumulated amortization	$ 55,665	$ 42,056
Voting units
Members' Equity Units, Authorized	100	100
Members' / stockholders' equity units issued (in units)	100	100
Members' / stockholders' equity units outstanding (in units)	100	100
Non-voting units
Members' Equity Units, Authorized	100	100
Members' / stockholders' equity units issued (in units)	100	100
Members' / stockholders' equity units outstanding (in units)	100	100