Commitments and Contingencies (Rental Expense Under Operating Leases) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Commitments and Contingencies [Abstract]
Rent expense	$ 2,119,348	$ 2,625,645	$ 4,167,722	$ 5,389,482
Less: Sublease income	(498,763)	(555,780)	(995,536)	(1,140,812)
Total rent expense, net	$ 1,620,585	$ 2,069,865	$ 3,172,186	$ 4,248,670