Dividends - Dividend Payments (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Jun. 30, 2013
Dividends [Abstract]
Cash dividend paid per common share (in dollars per share)	$ 0.17250	$ 0.17125
Total cash dividends paid	$ 12,186	$ 12,077	$ 24,263	$ 22,931
Record date	May 23, 2014	Feb. 21, 2014
Payment date	Jun. 27, 2014	Mar. 28, 2014