Employee Benefits (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair value of plan assets and major categories
Total, fair value of plan assets	$ 23,983	$ 20,517
Fair value of plan assets, Percentage	100.00%	100.00%
Fair Value Measurements Level 1 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	9,807	14,509
Fair Value Measurements Level 2 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	12,485	4,486
Fair Value Measurements Level 3 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	1,691	1,522
Collective funds [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	12,593	10,491
Fair value of plan assets, Percentage	52.50%	51.10%
Collective funds [Member] | Fair Value Measurements Level 1 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	767	6,657
Collective funds [Member] | Fair Value Measurements Level 2 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	11,826	3,834
Collective funds [Member] | Fair Value Measurements Level 3 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets
Equity securities [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	5,892	4,934
Fair value of plan assets, Percentage	24.60%	24.10%
Equity securities [Member] | Fair Value Measurements Level 1 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	5,892	4,934
Equity securities [Member] | Fair Value Measurements Level 2 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets
Equity securities [Member] | Fair Value Measurements Level 3 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets
Mutual funds [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	3,370	2,918
Fair value of plan assets, Percentage	14.10%	14.20%
Mutual funds [Member] | Fair Value Measurements Level 1 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	3,086	2,918
Mutual funds [Member] | Fair Value Measurements Level 2 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	284
Mutual funds [Member] | Fair Value Measurements Level 3 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets
Hedge funds [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	1,691	1,522
Fair value of plan assets, Percentage	7.00%	7.40%
Hedge funds [Member] | Fair Value Measurements Level 1 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets
Hedge funds [Member] | Fair Value Measurements Level 2 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets
Hedge funds [Member] | Fair Value Measurements Level 3 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	1,691	1,522
Short-term investments [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	437	652
Fair value of plan assets, Percentage	1.80%	3.20%
Short-term investments [Member] | Fair Value Measurements Level 1 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	62
Short-term investments [Member] | Fair Value Measurements Level 2 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets	375	652
Short-term investments [Member] | Fair Value Measurements Level 3 Inputs [Member]
Fair value of plan assets and major categories
Total, fair value of plan assets