Investment in Securities (Tables)

12 Months Ended

Dec. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-sale Securities

The amortized cost, gross unrealized gains, gross unrealized losses and fair value of debt and equity securities are summarized as follows:

	December 31, 2016
			Gross		Gross
	Amortized		Unrealized		Unrealized
(In thousands)	Cost		Gains		Losses		Fair Value
State and political subdivisions	$	368,223	$	5,239	$	3,328	$	370,134
U.S. government agencies		13,075		—		403		12,672
Certificates of deposit		7,746		—		—		7,746
Total	$	389,044	$	5,239	$	3,731	$	390,552
	December 31, 2015
			Gross		Gross
	Amortized		Unrealized		Unrealized
(In thousands)	Cost		Gains		Losses		Fair Value
State and political subdivisions	$	356,531	$	12,552	$	13	$	369,070
Certificates of deposit		6,626		—		—		6,626
Total	$	363,157	$	12,552	$	13	$	375,696

Schedule of Fair Value of Securities with Unrealized Losses

The fair values of securities with unrealized losses are as follows:

					December 31, 2016
	Less than 12 months				12 months or more					Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
(In thousands)	Fair Value		Losses		Fair Value		Losses		Fair value		Losses
State and political	$	140,384	$	3,328	$	—	$	—	$	140,384	$	3,328
subdivisions
U.S. government agencies		12,672		403		—		—		12,672		403
Certificates of deposit		—		—		—		—		—		—
Total	$	153,056	$	3,731	$	—	$	—	$	153,056	$	3,731
					December 31, 2015
	Less than 12 months				12 months or more				Total
	Estimated		Unrealized		Estimated		Unrealized		Estimated		Unrealized
(In thousands)	Fair Value		Losses		Fair Value		Losses		Fair value		Losses
State and political	$	3,638	$	5	$	1,208	$	8	$	4,846	$	13
subdivisions
Certificates of deposit		—		—		—		—		—		—
Total	$	3,638	$	5	$	1,208	$	8	$	4,846	$	13

Schedule of Amortized Cost and Fair Value

	December 31, 2016
(In thousands)	Amortized Cost		Fair Value
Due in 1 year or less	$	33,890	$	34,125
Due after 1 year through 5 years		57,536		58,414
Due after 5 years through 10 years		156,163		159,366
Due after 10 years		141,455		138,647
No stated maturity		—		—
Total	$	389,044	$	390,552