Investments (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Schedule of Investments and Restricted Investments

At December 31, 2017, 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	$	9,892	$	—	$	22	$	9,870
Corporate debt securities	67,781		411		1,817		66,375
Preferred stock	35,955		423		1,355		35,023
	113,628		834		3,194		111,268
Restricted investments:
Short-term bond	4,264		—		13		4,251
Money market fund	218		—		—		218
	4,482		—		13		4,469
	$	118,110	$	834	$	3,207	$	115,737

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

Continuous Unrealized Loss Position

The following table provides the U.S. Treasury securities, corporate debt securities, preferred stock and restricted investments unrealized loss position and related fair values:

	As of December 31, 2017								As of December 31, 2016
	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	$	9,870	$	22	$	—	$	—	$	—	$	—	$	—	$	—
Corporate debt securities	15,515		691		29,595		1,126		64,516		1,410		6,971		359
Preferred stock	11,263		1,337		1,986		18		—		—		153		111
Restricted investments:
Short-term bond	—		—		4,251		13		4,226		6		—		—
	$	36,648	$	2,050	$	35,832	$	1,157	$	68,742	$	1,416	$	7,124	$	470

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, 2017, 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	$	11,892	$	11,852
Due after one year through five years	65,713		64,332
Due after five year through ten years	68		61
	77,673		76,245
Preferred stock	35,955		35,023
Restricted investments	4,482		4,469
	$	118,110	$	115,737