Components of Debt Obligations (Parenthetical) (Detail)
3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
6 3/4 % Senior Notes Due 2020    
Debt Instrument [Line Items]    
Interest percentage 6.75% 6.75%
Debt maturity period 2020 2020
6.0% Senior Notes Due 2022    
Debt Instrument [Line Items]    
Interest percentage 6.00% 6.00%
Debt maturity period 2022 2022