Income Taxes - Summary of Income Tax Contingencies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, opening balance	$ 3,113	$ 2,952	$ 2,790
Gross increases in tax positions taken in a prior year	83	347	518
Gross decreases in tax positions taken in a prior year	0	0	(51)
Gross increases in tax positions taken in the current year	260	865	520
Settlements with taxing authorities	0	(507)	0
Lapse of applicable statute of limitations	(680)	(544)	(825)
Unrecognized tax benefits, ending balance	$ 2,776	$ 3,113	$ 2,952