Employee Benefit Plans - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 plan	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Increase in defined benefit plan, benefit obligation	$ 45,000,000
Estimated future benefit payments expected to be paid in 2015	22,800,000
Estimated future benefit payments expected to be paid in 2016	24,000,000
Estimated future benefit payments expected to be paid in 2017	25,600,000
Estimated future benefit payments expected to be paid in 2018	27,600,000
Estimated future benefit payments expected to be paid in 2019	29,200,000
Total estimated future benefit payments expected to be paid for the five years ending 2024	167,900,000
Percentage of total contributions made to multi-employer plans	5.00%
Number of multi-employer pension plans	4
Number of multi-employer plans deemed significant	2
CWA/ITU
Defined Benefit Plan Disclosure [Line Items]
Multi-employer plan withdrawal liability	4,800,000
GCIU
Defined Benefit Plan Disclosure [Line Items]
Multi-employer plan withdrawal liability	6,500,000
Multi-employer Plans, Withdrawal Obligation, Present Value				4,100,000
Multiemployer Plans, Withdrawal Obligation, Period of Repayment	20 years
SERP
Defined Benefit Plan Disclosure [Line Items]
Amortization of actuarial gain (loss)	(300,000)	(400,000)	(300,000)
Current year actuarial gain (loss)	600,000	700,000	2,300,000
Settlement charge		1,100,000
Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Amortization of actuarial gain (loss)	(2,861,000)	(4,192,000)	(4,246,000)
Current year actuarial gain (loss)	(75,527,000)	52,063,000	(30,761,000)
Increase in defined benefit plan, benefit obligation	5,004,000	6,502,000	7,664,000
Minimum
Defined Benefit Plan Disclosure [Line Items]
Period of consideration for historical plan asset rate of return	10 years
Historical period considered	10 years
Maximum
Defined Benefit Plan Disclosure [Line Items]
Period of consideration for historical plan asset rate of return	15 years
Historical period considered	15 years
Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range	70.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations range	30.00%
Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected amortization of actuarial loss from accumulated other comprehensive loss into net periodic benefit costs	4,900,000
Forecast [Member] | SERP
Defined Benefit Plan Disclosure [Line Items]
Expected amortization of actuarial loss from accumulated other comprehensive loss into net periodic benefit costs	300,000
Expected contributions to benefit plans	1,000,000
Forecast [Member] | Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Expected contributions to benefit plans	$ 0