Share Based Compensation (Details 2) (USD $)	6 Months Ended
	Jun. 30, 2012
Restricted Stock RSU [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at January 1, 2012	$ 19.07
Balance at January 1, 2012, Shares	38,600
Granted, Shares	15,350
Granted, Weighted-Average Grant Date Fair Value	$ 20.60
Vested, Shares	(13,100)
Vested, Weighted-Average Grant Date Fair Value	$ 15.36
Balance at June 30, 2012	$ 20.84
Balance at June 30, 2012, Shares	40,850
PBRS [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at January 1, 2012	$ 15.36
Balance at January 1, 2012, Shares	1,956
Granted, Shares	0
Granted, Weighted-Average Grant Date Fair Value	$ 0.00
Vested, Shares	(1,956)
Vested, Weighted-Average Grant Date Fair Value	$ 15.36
Balance at June 30, 2012	$ 0.00
Balance at June 30, 2012, Shares	0
PUP Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at January 1, 2012	$ 23.02
Balance at January 1, 2012, Shares	95,500
Granted, Shares	115,100
Granted, Weighted-Average Grant Date Fair Value	$ 20.60
Vested, Shares	0
Vested, Weighted-Average Grant Date Fair Value	$ 0.00
Balance at June 30, 2012	$ 21.70
Balance at June 30, 2012, Shares	210,600