Investments (Tables)

6 Months Ended

Jun. 30, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments

At June 30, 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	$	174,367	$	197	$	—	$	174,564
Corporate debt securities	20,086		78		1,152		19,012
Preferred stock	22,930		—		236		22,694
	217,383		275		1,388		216,270
Restricted investments:
Money market fund	5,653		—		—		5,653
	$	223,036	$	275	$	1,388	$	221,923

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 June 30, 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	18,262		1,152		—		—		6,292		981		—		—
Preferred stock	22,694		236		—		—		208		57		—		—
	$	40,956	$	1,388	$	—	$	—	$	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 June 30, 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	$	174,367	$	174,564
Due after one year through five years	19,987		18,929
Due after ten years through fifteen years	99		83
	194,453		193,576
Preferred stock	22,930		22,694
Restricted investments	5,653		5,653
	$	223,036	$	221,923