Investments (Tables)

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

At March 31, 2016 investments and restricted 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	$	184,930	$	19	$	—	$	184,949
Corporate debt securities	9,546		11		1,117		8,440
Preferred stock	265		—		117		148
	194,741		30		1,234		193,537
Restricted investments:
Money market fund	5,651		—		—		5,651
	$	200,392	$	30	$	1,234	$	199,188

At December 31, 2015 investments and restricted 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	$	184,819	$	—	$	79	$	184,740
Corporate debt securities	7,273		—		981		6,292
Preferred stock	265		—		57		208
	192,357		—		1,117		191,240
Restricted investments:
Guaranteed income fund	7,072		—		—		7,072
	$	199,429	$	—	$	1,117	$	198,312

Continuous Unrealized Loss Position

The following table provides the debt securities and preferred stock unrealized loss position and related fair values:    

	As of March 31, 2016								As of December 31, 2015
	Less Than 12 Months				12 Months or Greater				Less Than 12 Months				12 Months or Greater
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Debt securities:
U.S. Treasury securities	$	—	$	—	$	—	$	—	$	184,740	$	79	$	—	$	—
Corporate debt securities	8,251		1,117		—		—		6,292		981		—		—
Preferred stock	148		117		—		—		208		57		—		—
	$	8,399	$	1,234	$	—	$	—	$	191,240	$	1,117	$	—	$	—

Contractual Maturities of Investments

The net carrying value and estimated fair value of investments and restricted investments classified as available-for-sale at March 31, 2016, 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	$	184,930	$	184,949
Due after one year through five years	9,448		8,359
Due after ten years through fifteen years	98		81
	194,476		193,389
Preferred stock	265		148
Restricted investments	5,651		5,651
	$	200,392	$	199,188