Benefit Plans (Schedule of Fair Value of Plan Assets by Measurement) (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 236,781
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	222,039
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14,742
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Cash and domestic money market funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,620
Cash and domestic money market funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,620
Cash and domestic money market funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Cash and domestic money market funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. Treasury obligations
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,675
U.S. Treasury obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. Treasury obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,675
U.S. Treasury obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. Government agencies
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,588
U.S. Government agencies | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
U.S. Government agencies | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,588
U.S. Government agencies | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,479
Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,479
Corporate bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Common stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33,851
Common stock | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33,851
Common stock | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Common stock | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Equity mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	41,706
Equity mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	41,706
Equity mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Equity mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Fixed income mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	117,485
Fixed income mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	117,485
Fixed income mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Fixed income mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Foreign mutual funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24,377
Foreign mutual funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24,377
Foreign mutual funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0
Foreign mutual funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0