Employee Retirement Plans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current target allocations
Target allocations (as a percent)	100.00%	100.00%
Contributory retirement (401(k)) savings plans
Company contributions	$ 156	$ 161	$ 147
Corson Plan
Employee retirement plans
Unfunded projected benefit obligation	10	290
Comprehensive income (loss), net of tax	197	64	(149)
Comprehensive income (loss), tax expense (benefit)	112	36	(85)
Contributions by the entity	0	151	18
Number of major components of plan assets	2
Pension plan assets at the fair value
Fair value of assets	1,981	1,892	1,664
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	2,182	2,151
Interest cost	77	89	104
Actuarial (gain) loss on plan assets	(159)	54
Benefits paid	(109)	(112)
Projected benefit obligation at end of year	1,991	2,182	2,151
Change in plan assets:
Fair value of plan assets at beginning of year	1,892	1,664
Employer contribution	0	151	18
Actual gain on plan assets	198	189
Benefits paid	(109)	(112)
Fair value of plan assets at end of year	1,981	1,892	1,664
Funded status
Underfunded status	(10)	(290)
Accumulated Benefit Obligation
Accumulated benefit obligation	1,991	2,182
Net liability recognized on the consolidated balance sheets
Accrued benefit cost	10	290
Weighted-average assumptions used in the measurement of benefit obligation
Discount rate (as a percent)	4.50%	3.64%
Expected long-term return on plan assets (as a percent)	7.00%	7.00%
Components of the net periodic benefit cost
Interest cost	77	89	104
Expected return on plan assets	(128)	(119)	(137)
Amortization of net actuarial loss	80	84	71
Net periodic benefit cost	29	54	38
Expected benefit payments
2014	122
2015	128
2016	127
2017	128
2018	133
2019-2023	718
Corson Plan | Level 1
Pension plan assets at the fair value
Fair value of assets	1,891	1,892
Change in plan assets:
Fair value of plan assets at end of year	1,891	1,892
Corson Plan | Equity securities and funds
Current target allocations
Target allocations, minimum (as a percent)	50.00%
Target allocations, maximum (as a percent)	70.00%
Corson Plan | Pooled equity funds
Current target allocations
Target allocations (as a percent)	55.10%	28.90%
Corson Plan | Pooled equity funds | Level 1
Pension plan assets at the fair value
Fair value of assets	1,092	547
Change in plan assets:
Fair value of plan assets at end of year	1,092	547
Corson Plan | Pooled fixed income funds
Current target allocations
Target allocations, minimum (as a percent)	25.00%
Target allocations, maximum (as a percent)	50.00%
Target allocations (as a percent)	36.70%	58.20%
Corson Plan | Pooled fixed income funds | Level 1
Pension plan assets at the fair value
Fair value of assets	728	1,101
Change in plan assets:
Fair value of plan assets at end of year	728	1,101
Corson Plan | Other investments
Current target allocations
Target allocations, minimum (as a percent)	0.00%
Target allocations, maximum (as a percent)	15.00%
Target allocations (as a percent)	7.60%	5.90%
Corson Plan | Other investments | Level 1
Pension plan assets at the fair value
Fair value of assets	150	112
Change in plan assets:
Fair value of plan assets at end of year	150	112
Corson Plan | Cash and cash equivalents
Current target allocations
Target allocations, minimum (as a percent)	0.00%
Target allocations, maximum (as a percent)	10.00%
Target allocations (as a percent)	0.60%	7.00%
Corson Plan | Cash and cash equivalents | Level 1
Pension plan assets at the fair value
Fair value of assets	11	132
Change in plan assets:
Fair value of plan assets at end of year	$ 11	$ 132