Defined Benfit Plan (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended									9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Quoted Prices in Active Markets for Identical Assets	Dec. 31, 2013 Quoted Prices in Active Markets for Identical Assets	Sep. 30, 2014 Significant Observable Inputs	Dec. 31, 2013 Significant Observable Inputs	Sep. 30, 2014 Significant Unobservable Inputs	Dec. 31, 2013 Significant Unobservable Inputs	Sep. 30, 2014 Equity Securities [Member]	Dec. 31, 2013 Equity Securities [Member]	Sep. 30, 2014 Fixed Income Securities [Member]	Dec. 31, 2013 Fixed Income Securities [Member]	Sep. 30, 2014 Cash and cash equivalents	Dec. 31, 2013 Cash and cash equivalents	Sep. 30, 2014 Cash and cash equivalents Quoted Prices in Active Markets for Identical Assets	Dec. 31, 2013 Cash and cash equivalents Quoted Prices in Active Markets for Identical Assets	Sep. 30, 2014 Cash and cash equivalents Significant Observable Inputs	Dec. 31, 2013 Cash and cash equivalents Significant Observable Inputs	Sep. 30, 2014 Cash and cash equivalents Significant Unobservable Inputs	Dec. 31, 2013 Cash and cash equivalents Significant Unobservable Inputs	Sep. 30, 2014 Actively Managed All Cap Equity		Dec. 31, 2013 Actively Managed All Cap Equity		Sep. 30, 2014 Actively Managed All Cap Equity Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Actively Managed All Cap Equity Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Actively Managed All Cap Equity Significant Observable Inputs		Dec. 31, 2013 Actively Managed All Cap Equity Significant Observable Inputs		Sep. 30, 2014 Actively Managed All Cap Equity Significant Unobservable Inputs		Dec. 31, 2013 Actively Managed All Cap Equity Significant Unobservable Inputs		Sep. 30, 2014 Actively Managed U.S. Large Cap Equity		Dec. 31, 2013 Actively Managed U.S. Large Cap Equity		Sep. 30, 2014 Actively Managed U.S. Large Cap Equity Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Actively Managed U.S. Large Cap Equity Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Actively Managed U.S. Large Cap Equity Significant Observable Inputs		Dec. 31, 2013 Actively Managed U.S. Large Cap Equity Significant Observable Inputs		Sep. 30, 2014 Actively Managed U.S. Large Cap Equity Significant Unobservable Inputs		Dec. 31, 2013 Actively Managed U.S. Large Cap Equity Significant Unobservable Inputs		Sep. 30, 2014 Actively Managed U.S. Mid Cap Equity		Dec. 31, 2013 Actively Managed U.S. Mid Cap Equity		Sep. 30, 2014 Actively Managed U.S. Mid Cap Equity Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Actively Managed U.S. Mid Cap Equity Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Actively Managed U.S. Mid Cap Equity Significant Observable Inputs		Dec. 31, 2013 Actively Managed U.S. Mid Cap Equity Significant Observable Inputs		Sep. 30, 2014 Actively Managed U.S. Mid Cap Equity Significant Unobservable Inputs		Dec. 31, 2013 Actively Managed U.S. Mid Cap Equity Significant Unobservable Inputs		Sep. 30, 2014 Actively Managed U.S. Small Cap Equity		Dec. 31, 2013 Actively Managed U.S. Small Cap Equity		Sep. 30, 2014 Actively Managed U.S. Small Cap Equity Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Actively Managed U.S. Small Cap Equity Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Actively Managed U.S. Small Cap Equity Significant Observable Inputs		Dec. 31, 2013 Actively Managed U.S. Small Cap Equity Significant Observable Inputs		Sep. 30, 2014 Actively Managed U.S. Small Cap Equity Significant Unobservable Inputs		Dec. 31, 2013 Actively Managed U.S. Small Cap Equity Significant Unobservable Inputs		Sep. 30, 2014 Actively Managed Non-U.S. Large Cap Equity		Dec. 31, 2013 Actively Managed Non-U.S. Large Cap Equity		Sep. 30, 2014 Actively Managed Non-U.S. Large Cap Equity Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Actively Managed Non-U.S. Large Cap Equity Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Actively Managed Non-U.S. Large Cap Equity Significant Observable Inputs		Dec. 31, 2013 Actively Managed Non-U.S. Large Cap Equity Significant Observable Inputs		Sep. 30, 2014 Actively Managed Non-U.S. Large Cap Equity Significant Unobservable Inputs		Dec. 31, 2013 Actively Managed Non-U.S. Large Cap Equity Significant Unobservable Inputs		Sep. 30, 2014 Actively Managed REIT		Dec. 31, 2013 Actively Managed REIT		Sep. 30, 2014 Actively Managed REIT Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Actively Managed REIT Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Actively Managed REIT Significant Observable Inputs		Dec. 31, 2013 Actively Managed REIT Significant Observable Inputs		Sep. 30, 2014 Actively Managed REIT Significant Unobservable Inputs		Dec. 31, 2013 Actively Managed REIT Significant Unobservable Inputs		Sep. 30, 2014 Fixed Income		Dec. 31, 2013 Fixed Income		Sep. 30, 2014 Fixed Income Quoted Prices in Active Markets for Identical Assets		Dec. 31, 2013 Fixed Income Quoted Prices in Active Markets for Identical Assets		Sep. 30, 2014 Fixed Income Significant Observable Inputs		Dec. 31, 2013 Fixed Income Significant Observable Inputs		Sep. 30, 2014 Fixed Income Significant Unobservable Inputs		Dec. 31, 2013 Fixed Income Significant Unobservable Inputs
Components of Net Periodic Benefit Cost [Abstract]
Service cost	$ 1,056	$ 1,239	$ 3,167	$ 3,717
Interest cost	1,651	1,475	4,954	4,425
Other cost	627	1,208	1,883	3,624
Expected return on assets	(1,670)	(1,380)	(5,011)	(4,140)
Net periodic benefit cost	1,664	2,542	4,993	7,626
Plan Assets [Abstract]
Fair value of plan assets	99,004		99,004		95,353	58,753	55,532	40,251	39,821	0	0					7,261	9,127	7,261	9,127	0	0	0	0	2,402	[1]	283	[1]	2,378	[1]	266	[1]	24	[1]	17	[1]	0	[1]	0	[1]	35,541	[1]	32,286	[1]	35,541	[1]	32,286	[1]	0	[1]	0	[1]	0	[1]	0	[1]	5,731	[1]	5,551	[1]	5,731	[1]	5,551	[1]	0	[1]	0	[1]	0	[1]	0	[1]	3,010	[1]	3,236	[1]	3,010	[1]	3,236	[1]	0	[1]	0	[1]	0	[1]	0	[1]	4,832	[1]	5,066	[1]	4,832	[1]	5,066	[1]	0	[1]	0	[1]	0	[1]	0	[1]	4,480	[1]	3,913	[1]	0	[1]	0	[1]	4,480	[1]	3,913	[1]	0	[1]	0	[1]	35,747	[2]	35,891	[2]	0	[2]	0	[2]	35,747	[2]	35,891	[2]	0	[2]	0	[2]
Target plan asset allocations												55.00%	55.00%	45.00%	45.00%
Employer Contributions [Abstract]
Estimated employer contributions for the current fiscal year	5,946		5,946
Actual employer contribution amount in current period	$ 1,819		$ 3,638

[1] Actively managed portfolio of securities with the goal to exceed the stated benchmark performance.

[2] Actively managed portfolio of fixed income securities with the goal to exceed the Barclays 1-5 Year Government/Credit, Barclays Intermediate Government/Credit, and Merrill Lynch Preferred Stock Fixed Rate.