Variable Interest Entities (Details) - USD ($)				1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 11, 2012	Oct. 03, 2012	Aug. 30, 2011	Mar. 31, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Variable Interest Entity [Line Items]
Equity Method Investment, Other than Temporary Impairment					$ 12,593,000	$ 0	$ 12,593,000	$ 0
Next Generation Carrier-Class Communications Services Firm [Member]
Variable Interest Entity [Line Items]
Ownership percentage					40.80%		40.80%
Fair value of equity method investment					$ 0		$ 0
Equity Method Investment, Other than Temporary Impairment					12,600,000		12,600,000
Next Generation Carrier-Class Communications Services Firm [Member] | Other Current Assets [Member]
Variable Interest Entity [Line Items]
Notes receivable					3,000,000		3,000,000
Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Project fund							$ 59,300,000
Tax credit percentage							39.00%
Percentage of recapture							100.00%
Recapture period							7 years
Assets					140,900,000		$ 140,900,000		$ 140,900,000
Liabilities					$ 104,200,000		$ 104,200,000		$ 104,200,000
Primary Beneficiary [Member] | NMTC 1 [Member]
Variable Interest Entity [Line Items]
Project fund			$ 58,300,000
Interest rate percentage			1.00%
Primary Beneficiary [Member] | NMTC 1 [Member] | Minimum [Member]
Variable Interest Entity [Line Items]
Interest rate percentage			1.00%
Primary Beneficiary [Member] | NMTC 1 [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Interest rate percentage			3.96%
Primary Beneficiary [Member] | NMTC 2 [Member]
Variable Interest Entity [Line Items]
Project fund		$ 37,700,000
Interest rate percentage		1.00%
Primary Beneficiary [Member] | NMTC 2 [Member] | Minimum [Member]
Variable Interest Entity [Line Items]
Interest rate percentage		0.7099%
Primary Beneficiary [Member] | NMTC 2 [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Interest rate percentage		0.7693%
Primary Beneficiary [Member] | NMTC 3 [Member]
Variable Interest Entity [Line Items]
Project fund	$ 8,200,000
Interest rate percentage	1.00%
Primary Beneficiary [Member] | NMTC 3 [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Interest rate percentage	1.35%
Primary Beneficiary [Member] | US Bancorp [Member] | NMTC 1 [Member]
Variable Interest Entity [Line Items]
Amount to other entity			$ 22,400,000
Primary Beneficiary [Member] | US Bancorp [Member] | NMTC 2 [Member]
Variable Interest Entity [Line Items]
Amount to other entity		$ 17,500,000
Primary Beneficiary [Member] | US Bancorp [Member] | NMTC 3 [Member]
Variable Interest Entity [Line Items]
Amount to other entity	$ 3,800,000
Primary Beneficiary [Member] | Community Development Entities [Member] | NMTC 1 [Member]
Variable Interest Entity [Line Items]
Amount to other entity			$ 76,800,000
Primary Beneficiary [Member] | Community Development Entities [Member] | NMTC 2 [Member]
Variable Interest Entity [Line Items]
Amount to other entity		$ 55,200,000
Primary Beneficiary [Member] | Community Development Entities [Member] | NMTC 3 [Member]
Variable Interest Entity [Line Items]
Amount to other entity	$ 12,000,000
Variable Interest Entity, Not Primary Beneficiary [Member] | Next Generation Carrier-Class Communications Services Firm [Member]
Variable Interest Entity [Line Items]
Project fund				$ 3,000,000