Employee and Non-Employee Director Stock and Benefit Plans (Detail 5) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Additional disclosures
Tax shortfalls	$ 200,000
Restricted share awards
Total Number of Shares
Outstanding at the beginning of the period (in shares)	2,405,217	3,061,335	3,055,304
Granted (in shares)	1,458,673	990,801	1,392,746
Vested (in shares)	(1,123,720)	(1,203,142)	(1,050,760)
Forfeited (in shares)	(132,668)	(443,777)	(335,955)
Outstanding at the end of the period (in shares)	2,607,502	2,405,217	3,061,335
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 12.31	$ 13.25	$ 17.49
Granted (in dollars per share)	$ 15.45	$ 12.00	$ 10.63
Vested (in dollars per share)	$ 13.63	$ 14.47	$ 17.99
Forfeited (in dollars per share)	$ 12.10	$ 12.20	$ 26.10
Outstanding at the end of the period (in dollars per share)	$ 13.51	$ 12.31	$ 13.25
Additional disclosures
Unrecognized compensation costs	20,800,000
Weighted average period over which unrecognized compensation costs are expected to be recognized	1 year 11 months 5 days
Grant date fair value	18,600,000
Tax shortfalls related to the vesting	1,300,000	1,200,000	4,000,000
Tax shortfalls	400,000
Share-based compensation expense	15,000,000	13,000,000	12,400,000
Tax benefit related to share-based compensation expense	6,000,000	5,200,000	5,000,000
Market-based share awards
Total Number of Shares
Outstanding at the end of the period (in shares)	438,022
Performance-Based or Market-Based Restricted Stock Units
Total Number of Shares
Outstanding at the beginning of the period (in shares)	458,743	677,831	792,058
Granted (in shares)	219,644	91,932	216,740
Vested (in shares)	(145,786)	(64,865)	(86,769)
Forfeited (in shares)	(94,579)	(246,155)	(244,198)
Outstanding at the end of the period (in shares)	438,022	458,743	677,831
Time-Based Restricted Stock Units
Total Number of Shares
Outstanding at the beginning of the period (in shares)	1,946,474	2,383,504	2,263,246
Granted (in shares)	1,239,029	898,869	1,176,006
Vested (in shares)	(977,934)	(1,138,277)	(963,991)
Forfeited (in shares)	(38,089)	(197,622)	(91,757)
Outstanding at the end of the period (in shares)	2,169,480	1,946,474	2,383,504
Phantom share awards
Total Number of Shares
Outstanding at the beginning of the period (in shares)	671,762	695,710	397,747
Granted (in shares)		249,365	447,353
Vested (in shares)	(310,121)	(245,296)	(135,049)
Forfeited (in shares)	(3,292)	(28,017)	(14,341)
Outstanding at the end of the period (in shares)	358,349	671,762	695,710
Weighted Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 12.74	$ 13.72	$ 18.47
Granted (in dollars per share)		$ 12.01	$ 11.33
Vested (in dollars per share)	$ 14.06	$ 14.52	$ 19.46
Forfeited (in dollars per share)	$ 11.73	$ 14.92	$ 17.21
Outstanding at the end of the period (in dollars per share)	$ 11.61	$ 12.74	$ 13.72
Additional disclosures
Unrecognized compensation costs	2,300,000
Weighted average period over which unrecognized compensation costs are expected to be recognized	1 year 7 days
Market-based units
Total Number of Shares
Outstanding at the end of the period (in shares)	48,751
2007 Plan | Phantom share awards
Additional disclosures
Share-based compensation expense	3,500,000	7,300,000	2,600,000
Tax benefit related to share-based compensation expense	$ 900,000	$ 2,000,000	$ 700,000