Investments (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments and Restricted Investments

At December 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
Investments:
Corporate debt securities	$	135,590	$	5,311	$	1,769	$	139,132
Preferred stock	36,048		656		111		36,593
	171,638		5,967		1,880		175,725
Restricted investments:
Short-term bond	4,232		—		6		4,226
Money market fund	1,410		—		—		1,410
	5,642		—		6		5,636
	$	177,280	$	5,967	$	1,886	$	181,361

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
Investments:
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, preferred stock and restricted investments unrealized loss position and related fair values:

	As of December 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
Investments:
U.S. Treasury securities	$	—	$	—	$	—	$	—	$	184,740	$	79	$	—	$	—
Corporate debt securities	64,516		1,410		6,971		359		6,292		981		—		—
Preferred stock	—		—		153		111		208		57		—		—
Restricted investments:
Short-term bond	4,226		6		—		—		—		—		—		—
	$	68,742	$	1,416	$	7,124	$	470	$	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 December 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	$	3,910	$	3,719
Due after one year through five years	131,581		135,344
Due after ten through fifteen years	99		69
	135,590		139,132
Preferred stock	36,048		36,593
Restricted investments	5,642		5,636
	$	177,280	$	181,361