Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	9 Months Ended
	Jul. 31, 2014 Facility sqft	Sep. 30, 2014	Dec. 31, 2013
Commitments Contingencies And Guarantees [Line Items]
Leased office facilities expiration date		Jan. 31, 2032
Area under lease agreement	349,000
Aggregate rent expense in future years	$ 22,000,000
Term of capital lease	15 years
Number of existing facilities assigned to new lessor	1
Estimated lease incentives		35,670,000	33,209,000
Certain sales liabilities		5,800,000	5,800,000
Arlington [Member]
Commitments Contingencies And Guarantees [Line Items]
Estimated lease incentives		$ 55,000,000