Pension and Other Post-Retirement Benefit Plans (Fair Value of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 58,366	$ 55,474	$ 48,900
Real estate [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	29,717	26,057	19,561
Hedge funds and private equity [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	28,649	29,417	29,339
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	672,153	719,787	$ 751,246
Pension Plans [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	66,777	71,424
Pension Plans [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	547,010	592,889
Pension Plans [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	58,366	55,474
Pension Plans [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	672,153	719,787
Pension Plans [Member] | Common trust funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Common trust funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4,354	4,238
Pension Plans [Member] | Common trust funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Common trust funds [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4,354	4,238
Pension Plans [Member] | Corporate stock [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	14,832	17,878
Pension Plans [Member] | Corporate stock [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Corporate stock [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Corporate stock [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	14,832	17,878
Pension Plans [Member] | Mutual funds [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	46,991	51,568
Pension Plans [Member] | Mutual funds [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	99,056	100,252
Pension Plans [Member] | Mutual funds [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Mutual funds [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	146,047	151,820
Pension Plans [Member] | Fixed income investments [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	4,954	1,978
Pension Plans [Member] | Fixed income investments [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	443,600	488,399
Pension Plans [Member] | Fixed income investments [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Fixed income investments [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	448,554	490,377
Pension Plans [Member] | Real estate [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Real estate [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Real estate [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	29,717	26,057
Pension Plans [Member] | Real estate [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	29,717	26,057
Pension Plans [Member] | Hedge funds and private equity [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Hedge funds and private equity [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Pension Plans [Member] | Hedge funds and private equity [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	28,649	29,417
Pension Plans [Member] | Hedge funds and private equity [Member] | Total [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 28,649	$ 29,417