Share-Based Compensation - Summary of Restricted Stock and PBRS Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Restricted Stock
Summary of restricted stock and PBRS activity
Beginning Balance, Weighted-Average Grant Date Fair Value	$ 21.25	$ 20.36	$ 21.51
Beginning Balance, Shares	516,351	572,022	478,499
Granted, Shares	101,300	168,050	191,850
Granted, Weighted-Average Grant Date Fair Value	$ 27.27	$ 20.46	$ 22.70
Vested, Shares	(166,320)	(219,571)	(91,212)
Vested, Weighted-Average Grant Date Fair Value	$ 20.83	$ 18.26	$ 31.31
Forfeited or Cancelled, Shares	(20,432)	(4,150)	(7,115)
Forfeited or Cancelled, Weighted-Average Grant Date Fair Value	$ 22.13	$ 24.80	$ 20.81
Ending Balance, Weighted-Average Grant Date Fair Value	$ 22.78	$ 21.25	$ 20.36
Ending Balance, Shares	430,899	516,351	572,022
PBRS
Summary of restricted stock and PBRS activity
Beginning Balance, Weighted-Average Grant Date Fair Value	$ 0.00	$ 15.36	$ 33.02
Beginning Balance, Shares	0	416	18,830
Granted, Shares	0	0	0
Granted, Weighted-Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 0.00
Vested, Shares	0	(416)	(18,414)
Vested, Weighted-Average Grant Date Fair Value	$ 0.00	$ 15.36	$ 33.42
Forfeited or Cancelled, Shares	0	0	0
Forfeited or Cancelled, Weighted-Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 0.00
Ending Balance, Weighted-Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 15.36
Ending Balance, Shares	0	0	416