Restricted Stock Activity (Detail) (Restricted Stock Activity, USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Restricted Stock Activity
Number of Awards
Balance at beginning of period	1,028,844	1,310,619	758,049
Granted	166,125	156,450	599,526
Transferred from RSU	179,280
Vested	(362,100)	(396,786)	(24,156)
Forfeited	(18,837)	(41,439)	(22,800)
Balance at end of period	993,312	1,028,844	1,310,619
Weighted Average Grant Date Fair Value
Balance at beginning of period	$ 28.33	$ 24.97	$ 23.76
Granted	$ 41.28	$ 40.97	$ 26.50
Transferred from RSU	$ 42.35
Vested	$ 26.25	$ 22.27	$ 24.85
Forfeited	$ 31.49	$ 28.01	$ 24.95
Balance at end of period	$ 33.72	$ 28.33	$ 24.97