Investments (Tables)

3 Months Ended

Mar. 31, 2015

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

At March 31, 2015 investments classified as available-for-sale securities were as follows:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Debt securities:
Commercial paper (1)	$	248,294	$	60	$	—	$	248,354
U.S. Treasury securities	259,923		6		—		259,929
Corporate debt securities	101,973		—		780		101,193
Preferred stock	23,694		564		—		24,258
	633,884		$	630	$	780	$	633,734

(1) Recorded in Cash and cash equivalents on the Company’s Condensed Consolidated Balance Sheets.

At December 31, 2014 investments classified as available-for-sale securities were as follows:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Debt securities:
U.S. Treasury securities	$	509,783	$	32	$	—	$	509,815
Corporate debt securities	101,587		—		1,482		100,105
Preferred stock	26,963		—		5		26,958
	$	638,333	$	32	$	1,487	$	636,878

Contractual Maturities of Investments

The net carrying value and estimated fair value of investments classified as available-for-sale at March 31, 2015, by contractual maturity are shown in the following table. Actual maturities may differ from contractual maturities because certain borrowers have the right to call or prepay obligations.

	Amortized Cost		Fair Value
Due in one year or less	$	508,217	$	508,283
Due after one year through five years	101,973		101,193
	610,190		609,476
Preferred stock	23,694		24,258
	$	633,884	$	633,734