Capital and Accumulated Other Comprehensive (Loss) Income Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year			$ 664,106
Other comprehensive income	$ 4,252	$ (7,618)	(139)	$ (11,877)
Balance at end of year	791,267		791,267
Other Comprehensive Income (Loss), Tax			783
Reclassification From Accumulated Other Comprehensive Income, Current Period, Tax			(3,861)
Other comprehensive income	4,252	$ (7,618)	(139)	$ (11,877)
Unrealized gain on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year			83,137
Current period other comprehensive loss			13,432
Reclassifications, net of tax			(22,736)
Other comprehensive income			9,304
Balance at end of year	73,833		73,833
Other comprehensive income			9,304
Unrealized gain on derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year			0
Current period other comprehensive loss			9
Reclassifications, net of tax			0
Other comprehensive income			(9)
Balance at end of year	9		9
Other comprehensive income			(9)
Unrealized gain on derivative financial instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income			(2)
Other comprehensive income			(2)
Cumulative translation adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year			(4,691)
Current period other comprehensive loss			11
Reclassifications, net of tax			0
Other comprehensive income			(11)
Balance at end of year	(4,680)		(4,680)
Other comprehensive income			(11)
Change in net pension and other benefit obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year			(75,641)
Current period other comprehensive loss			1,076
Reclassifications, net of tax			0
Other comprehensive income			(1,076)
Balance at end of year	(74,565)		(74,565)
Other comprehensive income			(1,076)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of year			2,805
Current period other comprehensive loss			14,528
Reclassifications, net of tax			(22,736)
Other comprehensive income			8,208
Balance at end of year	$ (5,403)		(5,403)
Other comprehensive income			8,208
Unrealized gain on available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income			(7,972)
Other comprehensive income			(7,972)
Cumulative translation adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income			178
Other comprehensive income			178
Change in net pension and other benefit obligations
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income			(551)
Other comprehensive income			$ (551)