Income Tax Expense - NOL and Tax Credit Carryforwards (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
Federal [Member]
NOL and Tax Credit Carryforwards [Line Items]
NOL Carryforward	$ 279,800,000	[1]	$ 244,100,000	[1]
Tax Credit Carryforwards	35,500,000		16,000,000
NOL and Federal Tax Credit Carryforwards, Valuation Allowance	0
State [Member]
NOL and Tax Credit Carryforwards [Line Items]
NOL Carryforward	156,300,000	[1]	90,600,000	[1]
Tax Credit Carryforwards	11,900,000	[2]	10,300,000	[2]
State Tax Credit Carryforwards, Valuation Allowance	$ 7,700,000

[1] Pretax amounts

[2] Net of $7.7 million valuation allowance.