Investments (Tables)

12 Months Ended

Dec. 31, 2014

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

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

At December 31, 2013 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	$	124,861	$	88	$	—	$	124,949
Corporate debt securities	24,236		—		2,213		22,023
	$	149,097	$	88	$	2,213	$	146,972

Contractual Maturities of Investments

The net carrying value and estimated fair value of investments classified as available-for-sale at December 31, 2014, 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.

	Cost		Fair Value
Due in one year or less	$	509,783	$	509,815
Due after one year through five years	101,587		100,105
	611,370		609,920
Preferred stock	26,963		26,958
	$	638,333	$	636,878