Changes in Non-Vested Time Based Awards (Detail) (Time Based Restricted Stock Awards, USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Time Based Restricted Stock Awards
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Non-vested, beginning of period, Shares 1,176,890 952,920 885,482
Granted, Shares 1,570,393 811,080 488,634
Vested, Shares (559,763) (543,593) (374,351)
Forfeited, Shares (181,799) (43,517) (46,845)
Non-vested, end of period, Shares 2,005,721 1,176,890 952,920
Non-vested, beginning of period, Weighted Average Grant Date Fair Value $ 12.00 $ 14.11 $ 11.40
Granted, Weighted Average Grant Date Fair Value $ 10.31 $ 10.16 $ 16.88
Vested, Weighted Average Grant Date Fair Value $ 12.47 $ 12.83 $ 13.68
Forfeited, Weighted Average Grant Date Fair Value $ 11.15 $ 13.18 $ 14.51
Non-vested, end of period, Weighted Average Grant Date Fair Value $ 10.62 $ 12.00 $ 14.11