Accumulated Other Comprehensive Income - Reclassification Out of Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gain on investments																	$ (550)		$ (593)		$ (779)
Tax effect																	8,590		20,843		3,888
Amounts reclassified from AOCI, net of tax	(4,740)	[1]	10,849	[1]	6,253	[1]	8,065	[1]	(21,181)	[1]	19,976	[1]	5,451	[1]	1,027	[1]	20,558		5,959		9,292
Reclassification out of Accumulated Other Comprehensive Income | Unrealized Gains on Investments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Unrealized gain on investments																	99		92
Tax effect																	(38)		(35)
Amounts reclassified from AOCI, net of tax																	(61)		(57)
Reclassification out of Accumulated Other Comprehensive Income | Unrecognized Net Actuarial Loss and Service Credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect																	159		42
Recognized net actuarial gain (loss)																	(1,349)	[2]	(1,239)	[2]
Amortization of prior service credit																	902	[2]	1,113	[2]
Amounts reclassified from AOCI, net of tax																	$ (288)		$ (84)

[1] The fourth quarter of 2012 includes a tax charge of $13.4 million representing a valuation allowance for certain deferred tax assets associated with foreign tax credit carryforwards.

[2] (in thousands) 2013 2012 Affected Line Item in the Statement Where Net Income is PresentedUnrealized gains on investments $99 $92 Interest incomeTax effect (38) (35) Income taxes $61 $57 Net of tax Recognized net actuarial loss $(1,349) $(1,239) See Note 16Amortization of prior service credit 902 1,113 See Note 16Tax effect 159 42 Income taxes $(288) $(84) Net of tax