The following table summarizes fair value measurements by level at September 30, 2014, for assets and liabilities measured at fair value on a recurring basis:



	Level I		Level II		Level III		Total
Assets
Cash and cash equivalents	$	1,523,596	$	—	$	—	$	1,523,596
Investments available for sale:
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	270,857	$	39,715	$	—	$	310,572
Corporate securities	—		491,129		—		491,129
Municipal securities:
General obligation	—		49,875		—		49,875
Pre-refunded	—		4,985		—		4,985
Revenue	—		101,022		—		101,022
Variable rate demand notes	—		11,700		—		11,700
Asset backed securities	—		185,516		—		185,516
Mortgage backed securities	—		46,776		—		46,776
Total investments	$	270,857	$	930,718	$	—	$	1,201,575
Restricted deposits available for sale:
Cash and cash equivalents	$	78,995	$	—	$	—	$	78,995
Certificates of deposit	5,892		—		—		5,892
U.S. Treasury securities and obligations of U.S. government corporations and agencies	14,840		—		—		14,840
Total restricted deposits	$	99,727	$	—	$	—	$	99,727
Other long-term assets: Interest rate swap agreements	$	—	$	6,796	$	—	$	6,796
Total assets at fair value	$	1,894,180	$	937,514	$	—	$	2,831,694
Liabilities
Other long-term liabilities: Interest rate swap agreements	$	—	$	1,250	$	—	$	1,250
Total liabilities at fair value	$	—	$	1,250	$	—	$	1,250

The following table summarizes fair value measurements by level at December 31, 2013, for assets and liabilities measured at fair value on a recurring basis:



	Level I		Level II		Level III		Total
Assets
Cash and cash equivalents	$	974,304	$	—	$	—	$	974,304
Investments available for sale:
U.S. Treasury securities and obligations of U.S. government corporations and agencies	$	212,185	$	12,238	$	—	$	224,423
Corporate securities	—		296,086		—		296,086
Municipal securities:
General obligation	—		54,422		—		54,422
Pre-refunded	—		10,917		—		10,917
Revenue	—		69,054		—		69,054
Variable rate demand notes	—		28,575		—		28,575
Asset backed securities	—		139,050		—		139,050
Mortgage backed securities	—		33,891		—		33,891
Total investments	$	212,185	$	644,233	$	—	$	856,418
Restricted deposits available for sale:
Cash and cash equivalents	$	26,642	$	—	$	—	$	26,642
Certificates of deposit	5,891		—		—		5,891
U.S. Treasury securities and obligations of U.S. government corporations and agencies	14,413		—		—		14,413
Total restricted deposits	$	46,946	$	—	$	—	$	46,946
Other long-term assets: Interest rate swap agreements	$	—	$	9,576	$	—	$	9,576
Total assets at fair value	$	1,233,435	$	653,809	$	—	$	1,887,244