Marketable Securities and Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	$ 52,907	$ 39,331
Level I
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	52,906	39,284
Level II
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	1	47
Certificate of Deposit
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	2,318	2,858
Certificate of Deposit | Level I
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	2,318	2,858
U.S. Treasuries
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	50,082	35,918
U.S. Treasuries | Level I
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	50,082	35,918
Mutual Funds
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	506	508
Mutual Funds | Level I
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	506	508
Interest Rate Cap
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	1	47
Interest Rate Cap | Level II
Schedule Of Available For Sale Securities [Line Items]
Total Fair Value	$ 1	$ 47