Fair value of financial instruments (Tables)

9 Months Ended

Sep. 30, 2013

Fair value of financial instruments

Schedule of fair value of assets and liabilities measured on recurring basis

The following fair value hierarchy table presents information about each major category of our financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2013 (in thousands):

	Fair Value Measurement at Reporting Date Using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of September 30, 2013
Cash and cash equivalents	$	272,122	$	—	$	—	$	272,122
Certificate of deposit	15,024		—		—		15,024
Mortgage-backed securities	—		4,028		—		4,028
Total assets	$	287,146	$	4,028	$	—	$	291,174

The following fair value hierarchy table presents information about each major category of our financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2012 (in thousands):

	Fair Value Measurement at Reporting Date Using:
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2012
Cash and cash equivalents	$	224,057	$	—	$	—	$	224,057
Mortgage-backed securities	—		4,361		—		4,361
Total assets	$	224,057	$	4,361	$	—	$	228,418

Summary of marketable securities portfolio

	Amortized Cost		Net Unrealized Gains		Net Unrealized Losses		Estimated Fair Value
	(in thousands)
September 30, 2013
Certificate of deposit	$	15,024	$	—	$	—	$	15,024
Mortgage backed securities	2,020		2,008		—		4,028
	$	17,044	$	2,008	$	—	$	19,052
December 31, 2012
Mortgage backed securities	$	2,483	$	1,878	$	—	$	4,361
	$	2,483	$	1,878	$	—	$	4,361